United States
Environmental Protection
Agency
<&EPA Research and
Development
Annual Progress Report - Year 2
Fates and Effects of Herbicides
and Pesticides on Estuaries
Cooperative Research Program
Duke University
Dr. William Kirby-Smith, Principal Investigator
Gulf Breeze Environmental Research Laboratory
Dr, James R. Clark, Project Officer
Prepared by
Environmental Research
Laboratory
Gulf Breeze FL 32561
March 3, 1989
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Progress Report
to
U.S. Environmental Protection Agency
Environmental Research Laboratory
Gulf Breeze, FL 32561
Fates and Effects of Herbicides and Pesticides on Estuaries
Year 2 - Contract //CR 813415-01
from
William W. Kirby-Smith, Principal Investigator
Duke University Marine Laboratory
Beaufort, NC 28516
Contributing Investigators
William W. Kirby-Smith
Richard B. Forward
John D. Costlow
Duke University Marine Laboratory
Steven J. Eisenreich
Mark W. Sandstrom
Department of Civil and Mineral Engineering
University of Minnesota
Rick Luettich
Institute of Marine Sciences
University of North Carolina
February 24, 1989
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Progress Summary
Introduction
The second year of a project titled "Studies of the Fates and Effects
of Herbicides and Pesticides in Estuaries" has been completed in the South
River estuary, Carteret County, North Carolina. The research is a
cooperative effort among the following organizations: Duke University
Marine Laboratory, the Department of Civil and Mineral Engineering of the
University of Minnesota, Open Grounds Farm, Inc. and the Gulf Breeze
Environmental Research Laboratory of the U.S. Environmental Protection
Agency.
Field studies on the South River and adjacent Open Grounds Farm began
in the fall of 1986. The first annual progress report to EPA covered the
period August 1986 - July 1987. Research results presented here in this
second annual report cover the period August 1987 - July 1988. Included
below is a summary of the physical, chemical and biological studies which
have been accomplished during this period. As a measure of project
productivity we also include a list of papers which have been published,
are "in press" or are "in preparation" that are, in part or in whole, a
result of this project.
The South River' estuary is a shallow non-tidal embayment' of the
Pamlico Sound, 11 km in length, typical of many southeastern coastal plains
estuaries. Open Grounds Farm is a 44,186 acre agricultural development of
the Ferruzzi Group located in Carteret County, NC on a peninsula adjacent
to the Pamlico Sound and Neuse River estuarine system surrounding the South
River. The farm was established in 1974 on undeveloped land covered by
pine forest, swamp forest and pocosin. By 1980 development was completed
with approximately one third of the area lying in the South River
watershed. The farm grows grain crops (corn, soybeans, wheat) on 56% of
the total area, has pasture for cattle on 26% and has forest on 12%. The
remaining 6% is dedicated to roads, canals, field ditches, and buildings.
An essential part of farm development was the construction of a one-mile
grid of major drainage canals which serve to remove surface water and lower
the seasonal water table below the land surface. Although a forested
buffer was left around the South River the major drainage canals come
together and empty directly into the uppermost headwaters of several
tributaries of the estuary.
Based upon our two years of study we find that Open Grounds Farm and
the adjacent South River Estuary provide an excellent field site for the
study of the fates and effects of pesticides in estuaries. Farm management
has cooperated fully and allows access to all planting and pesticide
application records as well as providing physical access to the farm and
the estuary at all times: day, night, and weekends. Data suggest that
these studies will provide an excellent example of the influence on
adjacent estuaries of row crop agriculture which uses best management
practices (BMPs) in application of herbicides and pesticides.
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Research Results
Physical studies during this year have been aimed at development and
preliminary deployment of PSWIMS, a Profiling ^Shallow Water Instrument
Mounting System, to be used to give detailed descriptions of the
hydrography of the estuarine creeks receiving farm drainage. PSWIMS is a
computer-driven, self-contained system for continuous profiling of water
depth, salinity, and current velocity. Temperature and dissolved oxygen
measurements are being added. At the sites (1-2 m deep) where the
instrument is deployed it profiles the water quality parameter every
10 minutes using 7 depths scaled to give greatest resolution in surface
layers. The instrument is designed to provide two to four weeks of
continuous hydrographic data at upper estuarine sites where chemical and
biological studies of the fates and effects of pesticides are in progress.
The instrument is ideally suited for the temporal and spatial scales
involved in rainfall-mediated runoff events. The instrument performed
flawlessly for a one-month period in a research pond adjacent to the UNC
IMS Laboratory. Field deployment has been less successful because of
mechanical problems. However results to date from field studies have
demonstrated the utility of the data collected by the instrument. As an
example we observed velocity profiles on 4/7/88 which indicated surface
(top 10 cm) low salinity (5 ppt) runoff water moving downstream in the
estuary at a velocity of 2-10 cm/sec while there was an upstream movement
of saline (15 ppt) estuarine water at velocities of approximately
2.5 cm/sec in the remaining 1 m of the water column. Such information is
critical to our understanding of exposure of estuarine organisms to
herbicides and pesticides and to interpreting chemical samples taken in
surface and near bottom water samples. Development of PSWIM will continue
in the fall and winter 1988-89 to ensure its successful operation in the
spring 1989.
In chemical research two major field experiments examining the fates
of herbicides and pesticides were done during the last year. Runoff of the
pesticide permethrin was studied in August - September 1987 and runoff of
the herbicide alachlor was examined in April - May 1988. Analysis of the
alachlor experiments has not been completed and results of these studies
will be detailed in the next (third) annual report. The results of the
permethrin experiment are described below.
The pyrethroid insecticide permethrin was measured in the South River
estuary, North Carolina, during and following summer application on
adjacent farmland that drains into the estuary. Particulate material was
separated by filtration, and the dissolved compounds were isolated by solid
phase or liquid-liquid extraction and analyzed by GC-MS. The predominant
form of permethrin in all samples was in the particulate phase, generally
representing about 66% of the total. Maximum concentrations of 0.69 yg/L
particulate permethrin and 0.36 ug/L dissolved permethrin were measured in
farm drainage ditches immediately after application. Dilution of runoff
with estuarine water and other farm runoff resulted in maximum
concentrations of particulate permethrin of 0.08 pg/L in the estuary when
rainfall two days after application resulted in increased farm runoff.
Dissolved permethrin concentrations remained below detection limits at both
estuarine sites during the sampling period. The concentration of the
cis-permethrin isomer was greater than the trans-petmethrin in all samples,
representing 62-78% of the total. The measured distribution coefficients
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of permethrin in water from farm drainage ditches (1.2 - 7.0 x 10 L/kg)
were similar to that predicted (1.3 x 10 L/kg) from a simple equilibrium
adsorption model.
Biological studies in 1987-88 involved field and laboratory
investigation of the effects of alachlor, permethrin, and farm runoff in
general. Laboratory studies included (1) rearing of larval mud crabs
exposed to runoff, (2) effects of alachlor on 0^ consumption in mud crabs,
and (3) effects of alachlor on growth of phytoplankton (a dinoflagellate
and a diatom). Field studies included: (1) exposure of grass shrimp to
runoff, (2) nekton sampling in estuarine creeks, and (3) benthic community
analysis of estuarine creeks.
In laboratory studies the larvae of the mud crab Rhithropanopeus
harrisii were reared in two separate sets of experiments. In the first
experiment gravid females were exposed for a period of A days in estuarine
creeks, one receiving runoff from forest and the other receiving runoff
from permethrin-sprayed soybean fields. Larval survival from animals held
at the two sites did not differ from unexposed control animals. In a
second set of experiments gravid crabs were held in the laboratory for four
days in water from a ditch draining a permethrin-sprayed field and water
collected from a forest stream. In both cases the salinity of the water
was increased to 10 ppt by adding instant ocean. In neither case did
larval survival differ significantly from survival of controls.
Although laboratory projects were not considered a focus for research
in this current project we report here the results of three independent
study projects which developed because of our ongoing research on effects
of agricultural chemicals. Laboratory experiments with alachlor
concentrations of 10 and 25 ppm were used to investigate herbicide effects
on the respiration of adult mud crabs (Rhithropanopeus harrisii). While
decreased salinities caused O2 consumption to rise 30%, alachlor at
concentrations of 10 and 25 ppm had no effect on respiration. In
preliminary experiments the effects of alachlor on the growth of
phytoplankton (the diatom Skeletonema costatum and dinoflagellates
Prorocentrum micans) was examined. In Skeletonema studies concentrations
of .001, .01, .1 and 1 ppm were used. After 96 hours only 1 ppm had
significantly lowered growth rates compared to the control. In studies
using Prorocentrum micans alachlor concentrations of 0.1, 1, 10, and 50 ppm
were used in 96-h experiments. Significant inhibition of growth occurred
at alchlor concentrations of 1 ppm or greater.
Grass shrimp (Palaemonetes pugio) were held in 3 experiments in
estuarine creek runoff from fields sprayed with permethrin and a control
creek receiving only forest drainage. Mortality ranged from minimum 40% in
one control experiment to a high of 100% in two field runoff experiments.
Effects could not be attributed to runoff because of extremes in salinity
(runoff creek, 0 ppt) and dissolved oxygen (both creeks) experienced by the
animals. These preliminary results were used in planning late summer 1988
bioassay which will include holding animals in cages with an air/water
interface further downstream. In addition field bioassays are planned in
which larval shrimp will be raised in runoff-¦ from fields receiving
pesticide applications.
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Nekton communities were sampled by trawl in six tributary creeks of
the South River in the fall of 1987. Four creeks receive forest drainage
while 2 creeks receive farm drainage. Communities were dominated by bay
anchovy, spot and mullet. A comparison of farm runoff with forest runoff
creeks indicated no significant differences in total catch by weight or
numbers and that communities were basically identical. Preliminary
analysis of trawls taken weekly in the summer of 1988 in six creeks (three
with forest and three with farm runoff) suggest that nekton communities in
all creeks (with one exception) were similar in number, biomass and
community structure. The exception was one farm runoff creek which
differed from the other in having dramatically fewer bay anchovies
throughout the summer sampling period. Absence of anchovies remains
unexplained at this time.
Benthic community studies were done during the summer of 1988 in the
same six creeks as the nekton studies. Preliminary analysis of data
indicates that there is no difference among creeks in fauna (species
presence, abundance, or community structure) related to whether or not the
creeks receive farm runoff. All communities were similar at the 85% level.
At 94-97% similarity communities were related to each other in pairs by
their geographic location within the South River Estuary.
Publications
Published
Takacs, R.L., R.B. Forward, Jr. and W. Kirby-Smith. 1988. Effects of
alachlor on larval development of the mud crab, Rhithropanopeus harrisii
(Gould). Estuaries 11:79-82.
In press
Diamond, D.W. and R.B. Forward. Effects of salinity and the herbicide
alachlor on the respiration of the mud crab Rhithropanopeus harrisii
(Gould). Comparative Physiology and Biochemistry
In preparation
Costlow, J.D. and D. Gunster. 1988. Sublethal effects of the herbicide
alachlor on the mud-crab Rhithropanopeus harrisii (Gould).
Forward, R.B., Jr., W. Kirby-Smith, S.J. Eisenreich and J. Howe. Larvae of
the grass shrimp (Palaemonetes pugio) as a bioassay for the effects of
agricultural runoff in estuaries.
Kirby-Smith, W. and S. Thompson. The effects of agricultural runoff on the
benthic and nektonic communities in a tributary of the Pamlico Sound
estuarine system.
Sandstrom, M.W., S.J. Eisenreich and W. Kirby-Smith. Alachlor from
agricultural runoff in South River estuary, North Carolina.
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Sandstrom, M.S., S.J. Eisenreich and W. Kirby-Smith. Distribution of
permethrin from agricultural runoff in South River estuary, North Carolina.
Sommer, C.H., W. Kirby-Smith and R.B. Forward. Toxicity of the herbicide
alachlor to Atlantic silversides (Menidia menidia) and sublethal effects on
schooling behavior.
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Progress Report
to
U.S. Environmental Protection Agency
Environmental Research Laboratory
Gulf Breeze, FL 32561
Fates and Effects of Herbicides and Pesticides on
Estuaries: Chemical Analysis
Year 2-Contract # CR 813415-01
from:
Mark W; Sandstrom* and Steven J. Eisenreich
Environmental Engineering Sciences
Department of Civil and Mineral Engineering
University of Minnesota
Minneapolis, MN 55455
20 September 1988
* Present address: National Water Quality Laboratory, U. S.
Geological Survey, 5293 Ward Road, Arvada CO 80002
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Distribution of Permethrin from Agricultural Runoff in
South River Estuary, North Carolina
Mark W. Sandstrom* and Steven J. Eisenreich
Environmental Engineering Sciences
Department of Civil and Mineral Engineering
University of Minnesota
Minneapolis, MN 55455
* Present address: National Water Quality Laboratory, U. S.
Geological Survey, 5293 Ward Road, Arvada CO 80002
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Abstract- The pyrethroid insecticide permethrin, 3-
(phenoxybenzyl (1 RS)-c/'s,frans-3-(2,2-dichlorovinyl)-2,2-
dimethylcyclopropane-carboxylate, was measured in the South River
estuary, North Carolina, during and following summer application on
adjacent farmland that drains into the estuary. Particulate material
was separated by filtration, and the dissolved compounds were
isolated by solid phase or liquid-liquid extraction and analyzed by
GC-MS. The predominant form of permethrin in all samples was in
the particulate phase, generally representing about 66% of the total.
Maximum concentrations of 0.69 jig/L particulate permethrin and
0.36 jig/L dissolved permethrin were measured in farm drainage
ditches immediately after application. Dilution of runoff with
estuarine water and other farm runoff resulted in maximum
concentrations of particulate permethrin of 0.08 |ig/L in the estuary
even after rainfall 2 d post-application resulted in increased farm
runoff. The concentration of the c/'s-permethrin isomer was greater
than the frans-permethrin in all samples, representing 62-78% of
the total. The measured distribution coefficients of permethrin in
water from farm drainage ditches (1.2-7.0 x 10^ L/kg) were similar
to that predicted (1.3 x 10^ L/kg) from a simple equilibrium
adsorption model.
Keywords- Pesticides Nonpoint source pollution Estuaries
Permethrin GC-MS Distribution coefficient
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INTRODUCTION
Nonpoint source agricultural pollution - the runoff losses of
pesticides from agricultural fields - depends on a number of critical
factors, including rainfall timing, soil type, and the chemistry,
persistence and formulation of the pesticide (see Wauchope and
Leonard 1980; and Wauchope,1978 for reviews). While reasonable
estimates of the inputs of pesticides into adjacent rivers, lakes, or
estuaries can be made, information about the environmental fate and
effects of the pesticide is lacking. Assessments of the biological
effects usually depend on extrapolation of laboratory toxicity
studies. Similarly, predictions of the chemical behavior and fate are
made from laboratory studies or estimates based on chemical
structure and physical properties. These extrapolations from
laboratory studies generally do not account for the dynamics of
dilution, changes in ionic strength, or exchange with suspended
particles and organic colloids that occur when agricultural runoff
mixes with estuarine water.
The objective of this research was to characterize the
concentration and predominant forms of selected agricultural
chemicals in estuarine waters receiving agricultural runoff from
farms using best management practices. The South River estuary in
North Carolina was selected as the field study site. Most of the
watershed of the South River lies within Open Grounds Farm (OGF), a
45,000 acre agricultural enterprise developed into farmland by
construction of untiled drainage canals and field ditches.
Information about chemicals used, application rates, timing, and
access to the study site was providing by management of OGF.
Initial fieldwork for the project was conducted in spring 1987
during the planting of corn and the application of alachlor and
terbufos on fields adjacent to the estuary (Eisenreich and
Sandstrom, 1987). The work described in this report was conducted
during the summer of 1987 when permethrin was applied on soybean
fields in the Southwest Creek study area for the control of insects.
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Permethrin, 3-(phenoxybenzyl (1RS)-cis,trans-3-(2,2-
dichlorovinyl)-2,2-dimethylcyclopropane-carboxylate, is a widely
used synthetic pyrethroid insecticide sold under the trade names
"Pounce" (FMC Agricultural Chemical Group) or "Ambush" (ICI
Americas Inc.). Commercial formulations are mainly emulsifiabie
concentrates and contain variable mixtures of the isomers, generally
60% trans- and 40% c/s-permethrin (Sine et al.1987). It is generally
applied by ground or aerial spraying at a rate of about 0.2 kg/ha.
Permethrin has a low water solubility, ca. 0.2 mg/L, and a log K0w
of 5.70 (Muir et al. 1985a). Permethrin is of low mammalian toxicity
but is highly toxic to fish: the LC50 (96 h) for rainbow trout is 0.1-
0.5 jig/L (Swain and Tandy, 1984).
MATERIALS AND METHODS
Study Area
Southwest Creek is a small tributary of the South River, which
in turn is a shallow embayment of the lower Neuse River Estuary
(Figure 1). Mean tidal range in the South River is about 1 m, although
these are irregular tides caused by wind-induced set-up of Pamlico
Sound and the Neuse River Estuary; lunar tidal oscillations are only
1-2 cm. The main study sites focused on two sites within
Southwest Creek and one of the major drainage canals of a section
of Open Grounds Farm. The section of the estuary at Site SW4 was
about 20 m wide and 2 m deep, while Site SW4 was located further
upstream where the creek was about 3 m wide and 1 m deep. Site
DD12 was located in one of the large farm drainage ditches at the
headwaters of the creek. While this drainage ditch drained most of
the fields on which permethrin was applied in August 1987, drainage
ditches from other fields (which were not treated with permethrin)
also emptied into the headwaters of Southwest Creek. Also, this
drainage ditch was connected to the South River through another
outlet, so that the runoff from the fields in which permethrin was
applied was both diluted and diverted from our sampling sites.
Chemicals. All solvents were distilled in glass grade (Burdick
and Jackson Laboratories). An analytical reference standard of
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frans-permethrin was obtained from the U.S. E.P.A. Pesticides and
Industrial Chemicals Repository (MD-8), Research Triangle Park, NC.
d-(cis,trans)-Phenothrin [3-phenoxybenzyl 2,2-dimethyl-3-(2-
methylprop-1-enyl)cyclopropanecarboxylate] was obtained from
Chem Service, West Chester,PA. Stock solutions (1 mg/ml) were
prepared in hexane-dichloromethane (9:1) and stored at -10°C in a
freezer. Chrysene-di 2 was obtained from Supelco Inc. Working
calibration standards were prepared by dilution of the stock
solutions with hexane-dichloromethane (9:1) at five concentrations,
0.5, 2.5, 5.0, 10.0, and 25.0 ng/jil, and 5.0 ng/(il for Chrysene-d-j2.
Apparatus. A Hewlett-Packard 5985 mass spectrometer
coupled to a 5840A gas chromatograph and 21 MX E-Series data
system was used for all measurements. Calibration standards and
samples were injected manually. Compound separations were
performed on a fused silica capillary column 25 m x 0.31 mm i.d. (5%
phenylmethyl silicone, 0.52 film thickness, Hewlett-Packard) at
the following conditions: splitless injection at 80°C, isothermal for
2 min. followed by temperature programming at 20°C/min to 120°C
and then 10 °C/min. to 280°C; injector temperature and transfer line
temperatures of 250°C. The mass spectrometer operating conditions
were ion source temperature at 200°C, electron energy of 70 eV, and
selected ion monitoring mode (SIM) for characteristic ions at m/z
183, 123, and 240. Each ion was sampled for 75 ms for a total scan
time of 600 ms.
Field Sampling Procedures Samples were collected in
Southwest Creek from locations shown in Figure 1. Daily samples
were collected from Sites SW4, SW3 and DD12 from 12-16 August.
Application of permethrin on fields north of Southwest Creek by
aerial spraying occurred on the morning of 13 August 1987.
Samples were collected for suspended particulate material
(SPM), dissolved organic carbon (DOC) and chloride by pumping
estuarine water directly into a 2 L bottle. An aliquot of this sample
was filtered through pre-weighed 0.4 jim Nuclepore filters, and the
weight of suspended solids determined after drying.
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Six to eight liter water samples for XAD-2 resin adsorption
were collected at Sites SW3 and SW4 by pumping estuarine water
through 90 mm dia. GF/F glass fiber filters at a flow rate of 200
ml/min. using a submersible pump (March Manufacturing, Inc.; Model
893-02 seal-less magnetic pump). The pump inlet was located 2-4
cm below the water surface in order to sample the runoff water
above the halocline. Dissolved pesticides that passed through the
filters were stored in 20 L glass bottles until isolation in the field
laboratory, generally within 2-3 hrs after collection. The filters,
which retained particulate pesticides, were spiked with
approximately 500 ng of the field surrogate phenothrin, wrapped in
aluminium foil and stored in a freezer until subsequent extraction
and analysis.
Samples for liquid-liquid extraction (LLE) of pesticides were
collected at Site DD12 by submerging 2 L glass bottles below the
water surface and removing the caps. These samples were returned
to the field laboratory and stored in a refrigerator until filtration
through 47 mm dia GF/F glass fiber filters. Most samples were
processed within 2 hrs of collection.
Laboratory Procedures In the field laboratory, the 6-8 L
samples were spiked with the field surrogate phenothrin (about 300
ng/L) and the dissolved pesticides were isolated by pumping through
glass columns (2.5 x 30 cm) containing 150 ml of XAD-2 resin at a
flow rate of 100-120 ml/min . The columns were capped, returned
to the laboratory, and Soxhlet extracted with methanol for 24 hrs
followed by dichloromethane for 24 hrs. The 1-2 liter samples from
Site DD12 were spiked with the field surrogate permethrin (400-
600 ng/L), extracted with 20 ml dichloromethane-methanol (2:1)
followed by 2 X 20 ml dichloromethane. The dichloromethane layers
were combined, stored in a refrigerator, and returned to the
laboratory.
The dichloromethane layers and Soxhlet extracts were
partitioned against water, reduced in volume on .a rotary evaporator,
and dried by passage through a column of Na2S04. The total extracts
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were concentrated to about 100 jil with a gentle stream of nitrogen
at 25 °C, and then the external GC-MS quantitation standard
(chrysene-di2-) was added prior to GC-MS analysis.
The wet filters containing particulate pesticides were placed in
in 50 ml glass centrifuge tubes and extracted by vigorous agitation
(1-2 min) with hexane:isopropanol (HIP) 3:2 (Hara and Radin,1978).
The tubes were centrifuged and the solvent extract poured off, and
the extraction was repeated 2-3 times. The extracts were
combined, dried by passage through short columns of Na2S04, and
then reduced to approximate^ ml using a rotary evaporator and
transferred to a glass vial. The total extract was taken to a few p.l
under a stream of nitrogen, and immediately dissolved in a known
volume of n-hexane.
The total particulate extracts were then fractionated on
columns (10 mm i.d. x 300 mm) of neutral aluminum oxide (3.5 g;.
Fisher 70-200 mesh; deactivated with 1% H2O) over silica (7.0 g;
Fisher 100-200 mesh, deactivated with 5% H2O) prepared by slurry
packing in n-hexane. The particulate extract was transferred to the
column and washed with 25 ml n-hexane to remove aliphatic
hydrocarbons (alkanes and alkenes). The pesticides were eluted with
diethyl ether: hexane 1:1 (25 ml). Each fraction was transferred to
clean glass vial, concentrated to about 100 nl with a gentle stream
of nitrogen at 25 °C, and then the external GC-MS quantitation
standard (chrysene-di2) was added prior to GC-MS analysis.
DOC was determined on a separate aliquot filtered through
GF/F glass fiber filters. DOC was measured using a Dohrmann Model
DC-80 total organic carbon analyzer and a Horiba Model PIR-2000
infrared analyzer. Inorganic carbon was removed from acidified
water samples by purging with C02-free nitrogen. Organic carbon
was then oxidized to CO2 with potassium persulfate in an ultraviolet
irradiation chamber and the resultant CO2 was analyzed by non-
dispersive infrared spectroscopy. Chloride was measured on diluted
samples by an automated spectrophotometric technique (US EPA,
1976) and then converted to salinity using the-'relationship between
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salinity and chlorinity for standard seawater (Grasshoff et al.,
1983). Estimates of operational accuracy and precision for all of
these techniques are less than ±10 %.
Quantitation. The most intense ions in the mass spectra of
permethrin (m/z 183) and phenothrin (m/z 123) were chosen for
quantitation using the selected ion-monitoring (SIM) technique. Each
of the 5 calibration mixtures was analyzed each day during a sample
run and the mean relative response of each compound was
determined from quantitation of ion peak areas and injected
quantities of calibration mixtures and the external standard,
chrysene-d^.
Method Characteristics Recoveries of the field surrogate
phenothrin from filtered material averaged about 44% (range 28-
105%). Low recoveries can most likely be attributed to losses from
adsorption to silica-alumina columns in the sample clean-up step.
Phenothrin recoveries from 1-2 L liquid-liquid extracts were from
44-55%. However, phenothrin recoveries were less than 1% from the
6-8 L samples passed through XAD-2 columns. Previous work has
demonstrated good recoveries from reagent water and spiked
samples using this technique (Eisenreich and Sandstrom.1987). GC-
MS analysis of the XAD extracts indicated the samples contained
fatty acids and alcohols derived from estuarine organisms,
suggesting that there were no problems with the efficiency of the
XAD-2 columns in isolation of hydrophobic organic compounds. One
possibility for low recoveries may be that the 20 L glass sample
bottles were not rinsed with solvent after the samples were pumped
through the resin columns. Phenothrin (as well as permethrin and
other synthetic pyrethroids) is hydrophobic and will adsorb onto
glass surfaces from aqueous solution (Swain and Tandy 1984,
Sharom and Solomon, 1981b).
RESULTS
Hydrology
Previous fieldwork (Kirby-Smith and Barber, 1979, Eisenreich
and Sandstrom, 1987) has shown that runoff from rainfall results in
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increases in salinity stratification and an overall decrease in
bottom salinity in the estuary. The thickness and salinity of the
surface layer varies in response to freshwater runoff, tides (water
level), and wind speed and direction.
A 12 mm rainfall event on 10 August resulted in a significant
amount of freshwater in the estuary at the start of the fieldwork
(Figure 2). During this period the water column at Site SW3 was
characterized by a salinity gradient consisting of a 10-20 cm thick
layer of low salinity water (salinity = 2-4 ppt) above more saline
bottom water (salinity - 10-13 ppt). At Site SW4 the entire 1 m
water column was fresh throughout the sampling period. The
surface salinity at Site SW3 gradually increased as freshwater
runoff subsided and in response to northerly winds until another
rainfall event of 8-10 Cm occurred on 1>f August after application
of permethrin (Figure 2).
Concentrations of suspended particulate matter (SPM) at Sites
SW3 and SW4 during the August sampling period ranged from 11-24
mg/L, with a mean value of 16 mg/L (Table 1). Suspended solids
increased slightly at SW3 and decreased at SW4 after the rainfall
event on 15 August. Dissolved and colloidal organic carbon (DOC)
was extremely high and variable in the farm drainage waters at Site
DD12 with daily values varying between 33 and 196 mg/L. DOC
concentrations were lower in the estuarine waters, with mean
concentrations of 50 ± 14 mg/L at Site SW4 and 33 ± 8 mg/L at Site
SW3. Since the salinity values at SW4 indicated very little dilution
with estuarine water, the lower values of DOC at SW4 compared to
DD12 may be the result of dilution by mixing with drainage from
other fields with farm waters having low DOC. For example, during
April 1987 DOC levels in farm drainage water from an adjacent area
of OGF were only about 10-12 mg/L (Eisenreich and Sandstrom,
1987).
Permethrin concentrations
Permethrin concentrations at all sites were below detection
limits (2-20 ng/L) prior to application. Daily Concentrations of
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dissolved and particulate permethrin at Site DD12 are shown in
Figure 3. About 5 h after application permethrin concentrations in
farm drainage water at Site DD12 were 692 ng/L particulate
permethrin and 356 ng/L dissolved permethrin, consisting of
approximately 66% and 61%, respectively, of the cis -permethrin
isomer. The following day particulate permethrin concentrations
had decreased to 93 ng/L, and dissolved permethrin to 44 ng/L, each
consisting of about 77 % of the cis -permethrin isomer. Drift from
the aerial application may have resulted in the initial transfer of
the permethrin to the drainage water, in addition to shallow seepage
flow from the fields.
Shallow groundwater flow was apparently sufficient to
transport particulate permethrin from the drainage ditch to the
estuarine sites also. Particulate permethrin concentrations at Site
SW4 increased from 6 ng/L about 4 h after aerial application on 13
Aug to 53 ng/L on 14 Aug (Figure 4). The percentage of the cis-
permethrin isomer was similar to that at Site DD12, about 65 % on
14 August and 88 % on 15 August. At Site SW3 further downstream,
particulate permethrin concentrations were below or just above
detection limits on 13 and 14 August. Dissolved permethrin
concentrations remained below detection limits at both estuarine
sites during the sampling period.
A 10 mm rainfall on the evening of 14 August resulted in
increased runoff of farm drainage water into the estuary on 15
August, as shown by the dramatic decrease in surface salinity at
Site SW3 (Figure 2). Runoff resulted in increased concentrations of
particulate permethrin at both estuarine Sites SW4 and SW3 (Figure
4), consisting of about 67 % of the cis -permethrin isomer.
However, dissolved permethrin concentrations remained below
detection limits at both estuarine sites. At the headwaters of the
estuary at Site DD12 the pesticide concentrations decreased to 52
ng/L particulate permethrin (consisting of about 65 % of the cis -
permethrin isomer) and 6 ng/L dissolved permethrin (consisting of
about 56 % of the cis -permethrin isomer) after the rainfall event.
-------
9
Discussion
These results have demonstrated that the concentration of
total (dissolved plus particulate) permethrin in agricultural runoff
was as high as 1 (ig/L immediately after application. Such high
concentrations in farm drainage water were most likely due to drift
from the aerial application, since there was no intervening rainfall
to wash the pesticide from the soybean plants. However, there was
sufficient flow of shallow groundwater from the fields to transport
the particulate permethrin to the estuary, where concentrations
were much lower because of dilution. This low flow of water from
the drainage ditch into the estuary probably also caused a gradual
flushing of the permethrin from the drainage ditch as indicated by
the decrease in concentration of particulate permethrin at Site DD12
and increase at Site SW4 on 14 August after application.
Dissolved permethrin concentrations in the drainage ditch
immediately following application were similar to levels known to
be toxic to aquatic organisms. Permethrin is acutely toxic to
macrozooplankton at levels of 0.5 ^g/L (Kaushik et al. 1985). A
concentration of 0.39 ]ig/L permethrin killed 50% of newly hatched
crawfish in 96 h in sediment-free water.
This work also demonstrated that the permethrin occurred
predominantly in the particulate phase (66%) less than 5 h after
application on the adjacent fields. Previous field studies have
demonstrated that deltamethrin, another synthetic pyrethroid,
rapidly partitioned into suspended sediments when applied directly
to water (Muir et al. 1985b). The percentage of particulate
permethrin in the drainage ditch increased to 90% after the rainfall
event, suggesting that pessticide in runoff after the rainfall event
consisted mainly particulate permethrin. This is consistent with
the fact that only particulate permethrin was observed in the
estuarine samples. However, low recoveries of the field surrogate
prevents any definitive interpretation of the particulate-water
partitioning of permethrin in these samples.
-------
1 0
For samples from the drainage ditch at Site DD12 where
results of dissolved and particulate determinations are more
reliable we can compare the observed partitioning into the
particulate phase with that predicted from a simple equilibrium
sorption model. The partition coefficient Kp can be expressed as
(CL/SS)
Kp =
Cd
where Cp is the concentration of pesticide on particles (jig/kg), Cd
is the dissolved concentration (}ig/L)p and SS is the dissolved solids
concentration (kg/L). Suspended solids in Southwest Creek ranged
from 9 to 25 mg/L during the sampling period (Table 1), and an
average value of 15 mg/L was used to calculate the particulate
permethrin concentration in jig/kg, and the Kp values for permethrin
at Site DD12 during August. The calculated Kp values for cis- and
frans-permethrin, which are shown in Figure 5, ranged from 1.2 to
7.0 x 105 L/kg (log Kp = 5.1-5.8).
These values can be compared to partition coefficients
predicted from simple reversible adsorption. The sorption of
hydrophobic organic compounds from water by sediment consists
primarily of partitioning into the sediment organic phase.
Karickhoff et al. (1979) expressed the partition coefficient of
aromatic and chlorinated hydrocarbons in terms of the organic
carbon content of the solids:
Kp = Koc * foe
where Koc is the partition coefficient expressed on an organic carbon
basis, and foc is the fractional organic carbon concentration. The
value of Koc was further related to the octanol-water partition
coefficient according to the following relationship:
Koc — 0.63 Kqw
-------
11
Using a value of 5.70 for log Kow (Muir et al. 1985a), the Kpcan
be estimated for a range of organic carbon concentrations (foc). The
predicted log Kp values for f0c values from 0.1 to 0.6 are 4.5 to 5.3,
and are shown in Figure 5. These predicted values are similar to the
log Kp values measured at Site DD12.
The results of this fieldwork also demonstrated that cis-
permethrin was the predominant isomer found in all samples,
consisting of 61-88% of the total, even though technical mixtures
generally contain frans-permethrin as the predominant isomer (Sine
et al.,1987). This suggests very rapid degradation of the trans
isomer soon after application. Other field studies have
demonstrated that the cis isomer is more stable than the trans
isomer toward chemical and biological degradation in soils (Sharom
and Solomon, 1981a; Jordan and Kaufman, 1986). The percentage of
the cis isomer increased on the second day after application,
supporting the hypothesis of rapid degradation of the trans isomer in
the dissolved and suspended particle phases. Samples collected
after the rainfall event had higher percentages of the cis isomer,
similar to that the day of application. This may have been the result
of slower degradation of the permethrin in the soils compared to
that in the water or suspended solids, assuming that particulate
permethrin in runoff after the rainfall event was derived mainly
from the soils.
Previous studies have shown that timing of rainfall after
application is one of- the most important factors in determining
runoff losses of pesticides from agricultural fields. In this study,
rainfall occurred 2 d after application, increasing the potential for
high concentrations of pesticide in the runoff (Wauchope, 1978).
Although we have no information on the runoff volume and
percentage loss of the applied pesticide, we can compare the
maximum concentrations observed in runoff with that predicted
from a simple empirical model. Wauchope and Leonard (1980)
developed a semiempirical prediction formula from literature data
on pesticides in runoff. The formula is based on the pesticide
-------
1 2
formulation, application rate and time elapsed between application
and runoff:
Ct = AR(1+ 0.44 t)"1-6
where Ct is the predicted concentration, A is the availability index
A for different classes of pesticides, R is the application rate, and t
is time (d) post-application.
Permethrin, as an emulsifiable concentrate applied to foliage,
would be assigned a value of A of 300-1000 ppb ha/kg. Using the
application rate of 0.21 kg/ha for permethrin during this field study,
the predicted concentration of permethrin in runoff 2 d post-
application would be 20-70 jig/L. This is about 2 orders of
magnitude greater than that observed at Site DD12. While Wauchope
and Leonard (1980) caution that this formula will generally
overestimate concentrations, we know that the runoff at Site DD12
was diluted with water from other fields not treated with
permethrin. The differences between that predicted and observed
may give some indication of the magnitude of this dilution, and in
turn our observations of maximum concentrations of permethrin in
the estuarine sites.
ACKNOWLEDGEMENTS
We thank Bill Kirby-Smith for provision of facilities and
generous support during all aspects of the fieldwork; Oregon,
Suzanne, and Judy for field assistance; and Jay Powers for
invaluable assistance in the laboratory.
-------
13
REFERENCES
Abel, P.D. and Garner, S. M. 1986. Comparison of median survival
times and median lethal exposure times for Gammarus Pulux exposed
to cadmium, permethrin, and cyanide. Water Res., 20, 579-582.
Eisenreich, S. J. 1987. The chemical limnology of nonpolar organic
contaminants: PCB's in Lake Superior. In 'Sources and Fates of
Aquatic Pollutants' (Edited by R. A. Hites and S. J. Eisenreich), pp
393-469. American Chemical Society, Washington, D. C.
Eisenreich, S. J. and Sandstrom, M. W. 1987. The fate and effects of
herbicides and pesticides in estuaries: Chemical analysis. Progress
Report to US EPA, Environmental Research Laboratory, Gulf Breeze,
FL, pp 30.
Grasshoff, K., Erhardt, M. and Kremling, K. 1983. Determination of
Salinity. In 'Methods of Seawater Analysis' (Edited by K. Grasshoff,
M. Ehrhardt, and K. Kremling), pp 31-59. Verlag Chemie, Weinheim,
FRG
Hara, A. and Radin, N. S. 1978. Lipid extraction of tissues with a
low-toxicity solvent., Anal. Biochem., 90, 420-426.
Jordan, E. G. and Kaufman, D. D. 1986. Degradation of cis- and trans-
permethrin in flooded soil. J. Agri. Food Chem., 34, 880-884.
Karickhoff, S. W., Brown, D. S. and Scott, T. A. 1979. Sorption of
hydrophobic contaminants on natural sediments. Water Research, 13
241-248.
Kaushik, N. K., Stephenson, G. L., Solomon, K. R. and Day, K. E. 1985.
Impact of permethrin on zooplankton in limnocorrals. Can. J. Fish.
Aquat. Sci., 42, 77-85.
Kirby-Smith, W. W. and Barber, R. T. 1979. The water quality
ramifications in estuaries converting forest to intensive
agriculture, Water Resources Research Institute of the University of
North Carolina, Raleigh, North Carolina, WRRI Report No. 148, pp 70.
Muir, D. C. G., Rawn, G. P., Townsend, B. E., Lockhart, W. L. and
Greenhalgh, R. 1985a. Bioconcentration of cypermethrin,
deltamethrin, fenvalerate, and permethrin by Chironomus tentans
larvae in sediment and water. Environ. Toxicol. Chem., 4, 51.
-------
1 4
Muir, D. C. G., Rawn, G. P. and Grift, N. P. 1985b. Fate of the
pyrethroid insecticide in small ponds: a mass balance study. J.
Agric. Food Chem., 33, 603-609.
Sharom, M. S. and Solomon, K. R. 1981a. Adsorption and desorption
of permethrin and other pesticides on glass and plastic materials
used in bioassay procedures. J. Fish. Aquat. Sci. 38, 199-204.
Sharom, M. S. and Solomon, K. R. 1981b. Adsorption-desorption,
degradation and distribution of permethrin in aqueous systems. J.
Agric. Food Chem., 29, 1122-1125.
Swain and Tandy, 1984. Permethrin. In: Analytical Methods for
pesticides and plant growth regulators, Vol XIII. Academic Press,
Inc., New York, pp. 103-120.
Wauchope, R. D. 1978. The pesticide content of surface water
draining from agricultural fields-a review. J. Environ. Qual., 7, 459-
472.
Wauchope, R. D. and Leonard R. A. 1980. Maximum pesticide
concentrations in agricultural runoff: a semiempirical prediction
formula. , J. Environ. Qual., 9, 665-672.
Willis, G. H. and McDowell, L. L. 1982. Pesticides in agricultural
runoff and their effects on downstream water quality. Environ.
Toxicol. Chem., 1, 267-279.
-------
1 5
List of Tables
Table 1. Concentrations of suspended particulate matter (SPM),
dissolved organic carbon (DOC), and dissolved and particulate
permethrin in samples from Sites DD12, SW4, and SW3 in
Southwest Creek during 12-16 August 1987.
List of Figures
Figure 1. Location map of Open Grounds Farm and Southwest Creek
sampling sites during August 1987.
Figure 2. Time series plots of (a) rainfall and (b) salinity at
Southwest creek during August 1987.
Figure 3. Daily concentrations of (a) dissolved and (b) particulate
cis-, trans-permethrin at farm drainage ditch Site DD12.
Aerial application of permethrin occurred about 4 h prior to
sample collection on 13 Aug.
Figure 4. Daily concentrations of particulate c/'s-, frans-permethrin
at sites (a) SW4 and (b) SW3 in Southwest Creek.
Figure 5. Distribution coefficients (Kp) of cis-, and trans-
permethrin at Site DD12from 13-15 August 1987. The log Kp
predicted for simple equilibrium adsorption to particles with
10 and 60% organic carbon are also shown.
-------
Table 1- Salinity, suspended solids (SS), dissolved organic
carbon (DOC), and permethrin concentrations in
Southwest Creek during August 1987.
Particulate Dissolved
Permethrin Permethrin
SS DOC cis- trans- cis- trans-
Date Salinity (mg/L) (mg/L) (ng/L)
Site DD12
2-Aug
0.1
6.9
40.3
ot
0
0
0
3-Aug
0.3
-
195.9
423.2
269.2
204.0
152.0
4-Aug
0.0
-
-
71.8
22.0
34.0
10.0
5-Aug
0.1
-
33.2
34.7
18.8
3.3
2.6
6-Aug
0.1
-
140.2
5.6
4.6
0
0
Qifp QUM
2-Aug
0.0
24.0
— Ol lt5 OVV't - -- --
33.9 0
0
0
0
3-Aug
0.1
20.9
72.2
4.1
2.2
0
0
4-Aug
0.1
12.8
53.4
41.7
11.7
0
0
5-Aug
0.0
1 3.1
52.2
52.1
26.8
0
0
6-Aug
0.1
11.3
42.5
5.8
2.4
0
0
2-Aug
1.4
-
42.0 0
0
0
0
3-Aug
2.9
15.7
24.8
0
0
0
0
4-Aug
4.5
13.3
23.8
0.3
0.2
0
0
5-Aug
0.4
18.2
39.3
26.5
12.5
0
0
6-Aug
0.5
20.0
34.5
5.4
2.1
0
0
fO concentration indicates below limit of detection.
-------
North
Carolina
-------
Rainfall at Open Grounds Farm, August 1988
Rain (mm)
14.00
12.00 ..
10.00 --
8.00
6.00 --
1-Aug 3-Aug
Permethrin application
H 1 P*+¦
H
11-Aug 13-Aug 15-Aug 17-Aug
2. A.
i/
-------
Southwest Creek 12-16 August 1987
Date
2- L>
-------
Particulate Permethrin
Site DD12
450.0 -r
400.0 -¦
Concentration
(ng/L)
cis-Perm
trans-Perm
12-Aug 13-Aug 14-Aug 15-Aug 16-Aug
Date
/
-------
Dissolved Permethrln Site DD12
250.0 -r
H cis-Perm
Hi trans-Perm
3 b
-------
Particulate Permethrin Site SW4
FifiU't 4 a.
(J
-------
Particulate Permethrin
Site SW3
J^l'oO\f£ J?
0
-------
Permethrln Distribution Coefficient (Kp)
5
4
log Kp 3
2
1
0
13-Aug 14-Aug 15-Aug
~ cis log Kp
~ trans log Kp
log Kp (foc=0.1)
•O* log Kd (foc=0.6)
iffilll
P'A!W""!I
Wmm
>< -
¦
iglply
k -
-------
DRAFT COPY
PROJECT ARIES PHYSICAL OCEANOGRAPHY COMPONENT - YEAR 2
Submitted by Rick Luettich, UNC Institute of Marine Sciences
This report is broken up into three sections:
(I) The development of PSWIMS, a Profiling Shallow Water Instrument
Mounting System.
(II) Summary and analysis of physical data collected during
April/May 19S8.
(III) Summary and analysis of physical data collected during
August 1988. (not completed)
(I) The development of PSWIMS, a Profiling Shallow Water Instrument
Mounting System
It is a commonly observed and predictable phenomenon that the water
column in a shallow waterbody does not behave as a layer which is
uniform over its depth. On the contrary, friction forces horizontal
velocities to zero at the bottom while they can be driven by the wind at
the free surface. In closed basins, density driven flows, and highly
transient flows, reversals in horizontal velocity may occur over the
depth. Vertical transport is predominantly due to molecular or
turbulent diffusion, both of which imply the existence of vertical
gradients of the quantity being diffused. Stratification tends to
inhibit vertical transport and further segregate parts of the water
column. For example strong temperature or salinity stratification can
Page 1
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effectively isolate bottom water from contact with the atmosphere and
allow it to become anoxic at the same time water above the gradient zone
is oxygen enriched.
Observational programs which attempt to quantify the behavior of
such waterbodies require instrumentation systems which can resolve these
vertical structures. In the past this has been dealt with in one of two
ways, either by manually raising and lowering a single set of
instruments over the depth of the water column or by mooring a vertical
array of instruments in the water column. Both methods have serious
drawbacks. The use of manual labor becomes impractical in rough weather
conditions and for long term studies which require frequent samplings.
It is also difficult to accurately suspend sensors over the side of a
boat in moderate currents or waves. Vertical arrays require the
purchase of multiple instrument sets and quickly become very expensive.
In these systems vertical resolution is often coarse and due to the
available budget, although even with unlimited funds the physical
dimensions of the sensor units ultimately limit their spacing. Also
moored instruments are by design fixed at a constant depth. Thus they
are inefficient in situations where temporal variations in the
waterlevel are significant in comparison to the total depth or in which
dense sampling is desired over a fraction of the water column (such as a
gradient zone) whose position varies in time.
The first year of field measurements for the ARIES project
illustrated these problems dramatically. Measurements were necessary in
water having mean depths ranging from 1-2 meters which were routinely
subject to 0.5 - 1.0 meter changes in water level over periods as short
as one day. Fresh water runoff typically occurred in a surface layer of
Page 2
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variable depth and salinity and at velocities which were difficult to
resolve from a boat using a hand held electromagnetic current meter.
Also runoff from a particular rainfall event was variable in time and
could extend for several days.
To overcome these problems PSWIMS, which stands for Profiling
Shallow Water Instrument Mounting System, has been developed. The
principal design considerations were the following:
(i) to be able to measure vertical profiles of physical and chemical
parameters (e.g., velocity, salinity, dissolved oxygen, etc.) over
intervals which are small in comparison to their timescale of variation,
(ii) to be able to make real time adjustments in measurement position in
response to changes in water level or to changes in elevation of
specific regions of interest (e.g.. gradient zones).
(iii) to be light and portable enough to be deployed and recovered from
a small boat (i.e., one which could easily be maneuvered in the narrow
and shallow creeks under study) without hoists or scuba divers.
(iv) to be capable of deployments for periods of weeks or longer.
(v) to be simple to build and as inexpensive as possible.
The heart of PSWIMS consists of a computer controlled, motor driven
sleeve which travels up and down a vertical shaft. Figure P0.I.1. The
motor is a reversible, 12 volt DC motor geared to run at 9 rpm and is
located in a water tight housing at the bottom of the vertical shaft.
The motor drive turns a set of two pulley wheels which simultaneously
take up and let out stainless steel wire. One end of the wire is
attached to the bottom of the sleeve while the other end is attached to
the top of the sleeve after passing over a single pulley wheel at the
top of the vertical shaft. In this configuration the sleeve can be
Page 3
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raised by running the motor in one direction and lowered by reversing
the motor.
The vertical shaft consists of 2 in. schedule 80 PVC pipe. The
1/4 in thick walls provide substantial rigidity while the PVC is light
weight, easily available and inexpensive. The sleeve consists of a 3
in. PVC "T" which fits over the 2 in. pipe with about 1 in. of total
clearance. Sixteen delrin ball bearings (eight at the top and eight at
the bottom) are located around the inner circumference of the sleeve
between it and the vertical shaft. The bearings are held in place by
two collars which are glued inside the PVC "T" at the top and the
bottom. The bearings serve as spacers to keep the sleeve parallel to
the shaft and to minimize frictional resistance by minimizing the
contact area between the sleeve and the shaft. A single thin strip of
plexiglass is glued along the length of the vertical shaft and serves as
a track to keep the sleeve from turning.
The water tight housing for the motor is constructed from a piece
of 6 in. I.D. schedule 40 PVC pipe. The back end is sealed by gluing
two circular pieces of 1/4 in. thick PVC over it. This provides a
convenient surface for mounting standard electrical bulkhead penetrators
to provide power and motor control. The front end consists of a 1/4 in.
thick piece of plexiglass which is sealed against the end of the PVC
pipe using an o-ring seal. It is held in place by four wing nuts which
are threaded onto studs attached to the outside of the PVC pipe. A
water pump from a 1974 Honda Civic automobile (after removing the
impeller blades and the drive wheel) is used as the part of the drive
shaft which penetrates the housing. This unit is mounted on the inside
of the front end of the housing and provides a fixed alignment as well
Page 4
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as a double seal for the drive shaft. The water pump shaft is coupled
on one end to the motor shaft and on the other end to the shaft through
the drive wheels using collars machined from delrin.
The assembly is controlled by a Tattle Tale model II data logger
(manufactured by Onset Computer Corp.) which also samples and stores
data from the various instruments mounted on PSWIMS. This little marvel
runs off a 6 - 10 volt DC supply, comes with an 8-channel, 8-bit A to D
converter which reaches full scale at 5 volts, 14 digital I/O lines, 16K
of program storage area, 224K of RAM for data storage, an RS-232C
interface and a built in basic interpreter. Programs can be uploaded
and data downloaded by connecting a PC directly to the RS-232C cable
which is provided. In the field this is easily accomplished using a
portable laptop computer.
The Tattle Tale digital lines are used to control relays which
switch power on and off to the motor as well as control its direction.
The sleeve position is determined using a 10K, 10 turn potentiometer
which is geared to the motor. A 5 volt reference is provided to one
side of the potentiometer and one of the Tattle Tale A/D channels is
used to measure the voltage on the wiper. This voltage is linearly
related to the sleeve position which is accurate to within the 8-bit
resolution of the A/D. In the present application a 236 cm long
vertical travel path is used allowing better than 1 cm accuracy.
As a safety feature, end of travel switches are mounted near the
top and bottom of the vertical shaft- These consist of magnetic
switches which are closed by magnets mounted on the top and the bottom
of the sleeve, should it reach these points. Closing either of these
switches shuts off the power to the motor.
Page 5
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The profiling system is mounted on an 8 ft. high by 6 ft. wide
frame made from 2 im PVC pipe, (Figure P0.I.2). The vertical shaft is
located in one corner so that an arm attached to the sleeve projects the
measurement sensors into the middle of the frame to minimize the effects
of flow disturbance induced by the frame. The actual design of the
frame is a compromise between stability and portability. PVC pipe is
used because it is inexpensive, easy to work with and is relatively
light weight. Each leg of the frame has a screw on cap at the top and
when all are in place the frame is water tight. When PSWIMS is deployed
the leg caps are removed and a valve at the base of the frame is opened
allowing water to fill the structure. Iron bars are then placed inside
the legs for weight. For recovery the iron bars are removed and the
caps are placed on each leg. The frame is then pumped full of air (the
water exits through the open valve at the bottom) using a battery
operated air pump. This greatly facilitates lifting PSWIMS onto the
recovery boat.
At present PSWIKS is instrumented with sensors to measure water
level, salinity and horizontal water velocity. Water level is measured
using a surface piercing sensor manufactured by the Metritape company.
This measurement is made and recorded just prior to beginning a vertical
profile and therefore is used to adjust the extent over which the
sampling is to be conducted. Salinity is measured using an Aandera
model 2975 salinity sensor and horizontal velocity is measured along two
axes using a Marsh McBirney model 512 electromagnetic current meter.
The electronics for the salinity meter come packaged in a small housing
attached to the sensor itself while those for the current meter have
been built into the arm on which the salinity and velocity sensors are
Page 6
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A \
S UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
ENVIRONMENTAL RESEARCH LABORATORY
%. ,\v
*1 fHCfl*- SABINE ISLAND
GULF BREEZE. FLORIDA 32961-3999
February 28, 1989
SUBJECT:
FROM:
TO:
THRU:
Enclosed are two copies of the second annual progress report
by the staff at Duke University on the cooperative research pro-
ject we have funded to investigate effects of pesticide runoff on
estuarine biota. The report covers hydrographic, chemical, and
biological factors covered in the fate and effect study of the
South River Estuary near Beaufort, NC. As we have discussed previ-
ously, results of this study are directly applicable to Region IV
interests in coastal, non-point source pollutant problems and the
comprehensive investigation underway in the Albemarle-Pamlico
Sound. We hope you find these data useful. We will continue to
keep you appraised of our progress in this endeavor.
Pesticide Runoff Study at .Beaufort, NC
James Clark
Acting Branch Chief-Ecotoxicology
Bruce Barrett
Director, Water Management Division
Raymond Wilhour
Acting Laboratory Director
This research program is being operated on a shoe-string
budget and could easily be expanded with additional resources. If
you have interest in this project and see a spin-off benefit and
have resources to cover changes to the project, please contact me.
Or, if you wish to discuss the prospects of expansion, I have some
ideas on how to approach non-point source nutrient inputs, silta-
tion effects, and other non-pesticide related research questions.
Enclosure
-------
mounted. The Tattle Tale, relays to turn the motor, the electromagnetic
current meter and the water level gauge on and off, and several signal
amplifying circuits are located in a small plexiglass and PVC housing
which is strapped to one corner of the frame.
Power to PSWIMS is provided by two 12 volt 40 Amp. Hr. rechargeable
batteries which are configured to provide + and - 12 volts to run the
motor down and up respectively and power the electromagnetic current
meter. The batteries are located in a watertight enclosure which can be
mounted on the upper rung of the PVC frame or placed on shore, depending
on the distance. A 9 volt radio battery in the data logger housing
functions as a back up for the Tattle Tale to prevent the loss of any
data stored in memory while the primary batteries are being changed or
if they should expire prematurely. The principal battery drain occurs
while the motor is raising the sleeve up the shaft. This can be as much
as 1.2 amps while the sleeve and attached sensor arm are out of the
water. However, because the sensor arm is nearly neutrally buoyant
under water, this is reduced to about 0.6 amps when the arm is
submerged. The Tattle Tale, water level sensor and electromagnetic
current meter each typically use less than 20 mA of current and the
power to the sensors is turned off when they are not in use. The Tattle
Tale is capable of monitoring the battery supply voltage and shutting
PSWIMS down if it drops below a preselected level.
The development of PSWIMS was begun in the latter part of year one
of the ARIES project with the intention of having it ready for use
during the year two April/Kay study. Early deployments of the system
were plagued by randomly occurring "glitches" which either destroyed
some of the amplifying circuitry associated with the vertical
Page 7
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positioning or even worse froze the Tattle Tale entirely. In the latter
case the operation of PSWIMS was completely disrupted and unfreezing
required that all power to the Tattle Tale be disconnected. This caused
any data which was in the data logger memory to be lost. Unfortunately
this problem was not fully solved until after the April/May study was
completed and therefore very little useful PSWIMS data was obtained.
However, the data which was obtained clearly showcases the capabilities
of PSWIMS.
Figure P0.I.3 shows data collected from 16:00 on 4/6 to 12:00 on
4/7 at site HR1 in Home Road Creek (see section II for a further
description). The variation in water level is shown along with plots of
salinity and horizontal velocity measured 0.76m above the bottom.
Unfortunately, a "glitch" had caused the loss of ability to position the
arm vertically and therefore it was left at a constant elevation. The
data in Figure P0.I.3 show why physical measurements at one elevation
are of minimal use in estuarine studies. Initially the salinity and
velocity data suggest that the sensors were measuring in a nearly fresh
water runoff layer. However at the beginning of 4/7 a rapid increase
occurred in water level. Correspondingly the salinity jumped to values
characteristic of near bottom water and the water velocity became
strongly upstream. Therefore it seems that the increase in water level
was sufficient to lift the fresh water runoff layer above the sensor
elevation and bring salty near bottom water which was flowing upstream
into contact with the sensors. Thereafter each drop in water level
brought the sensors into contact with the bottom of the downstream
flowing surface layer and each rise imbedded them in the upstream
flowing bottom layer.
Page 8
-------
The problem associated with the vertical positioning was corrected
on 4/7 and for the following 18 hours PSWIMS functioned normally. Figure
P0.I.4 presents the variation in water level from 16:00 on 4/7 to 10:00
on 4/8. For comparison water level measurements made simultaneously by
a Stevens tide gauge located a short distance away at the mouth of South
West Creek are also shown. The agreement is outstanding particularly
considering the tide gauge data was recorded on a strip chart and later
digitized by hand.
During this period PSWIMS was programmed to take a vertical profile
every 10 minutes. Each profile consisted of 7 points over the vertical
where the instruments were positioned and sampled for 30 seconds. Each
30 seconds of data was averaged and stored before proceeding to the next
elevation. Sampling was somewhat concentrated near the surface to
resolve the thin freshwater runoff layer which was expected. Figure
P0.I.4 shows a plot of the points where measurements were made during
this period. It illustrates clearly how PSWIMS is able to adapt its
sampling points to account for the varying water depth.
Figure P0.I.5 shows three salinity and velocity profiles which were
measured at the beginning of this period. They indicate downstream flow
in a freshwater surface layer and a weaker upstream flow in a salty
bottom layer.
Figure P0.I.6 is a composite vector plot of the velocity data from
each profile. The data shows a clear picture of the horizontal velocity
structure throughout the water column during this period. For the first
12 hours there is a mostly downstream surface flow and weak upstream
bottom flow. The downstream layer deepens at about 20-00 on 4/7 which
corresponds to a drop in water level (Figure P0.I.4) that
Page 9
-------
effectively pulls water downstream. Shortly after 4:00 on 4/8 the
surface velocity reverses and the entire water column moves strongly
upstream. This corresponds to a period of increasing water level which,
much like a tidal surge, pushes water ahead of it over the entire depth.
Figure P0.I.7 is a contour plot of the salinity data from each
profile. It shows the existence of a fresh water surface layer for the
first 12 - 14 hours which corresponds to the period of downstream
surface flow. It also shows that the rise in water level and the
accompanying upstream flow occurring after 4:00 on 4/8 is strong enough
to push vertically well mixed water from South West Creek up into Home
Road Creek, at least past the measurement site. This process is
discussed further in section II.
Further testing with PSWIMS during May uncovered the cause of the
troublesome "glitches" and these have now been eliminated. Since that
time PSWIMS was operated continuously for over 4 weeks in water 1 m deep
in a cement pond behind the UTJC Institute of Marine Sciences. At this
point I am confident of its mechanical and electronic integrity and
anticpate using it in August in conjunction with additional runoff
studies.
(II) Summary and analysis of physical data collected during
April/May 19S8
Summary of Observations:
Data was collected in two separate tributaries feeding into South
West Creek during the course of this study. From March 30 - April 21
Page 10
-------
sampling was conducted in Home Road Creek while from April 22 - May 9 it
was concentrated in the upstream sections of South West Creek, (Figure
P0.II.1).
(i) Home Road Creek Study, March 30 - April 21
Fic^ire P0.II.2 indicates that one major rainfall occurred during
this interval, leaving about 60 mm of rain over the two day period of
4/12 and 4/13. A moderate rainfall of between 15 and 20 mm fell on 4/6
while smaller events occurred on 4/4, 4/16 and 4/19.
Water level fluctuations measured at the mouth of the South West
Creek are shown in Figure P0.II.3. The most striking feature is the
high water which occurred on 4/13 and 4/14. At its peak it was more
than 1.3 m above the average elevation for the period and more than
1.5 m above the lowest recorded elevation. Unfortunately, this extreme
event, which overtopped the channel banks by more than 1.2 m. drowned
the automatic samplers thereby terminating the collection of samples for
salinity as well as other chemical analyses.
Six hour averages of the wind velocity measured about 30 km to the
southwest at the UNC Institute of Marine Sciences are presented in
Figure P0.II.4. While the distance between the wind measurement and the
field sites precludes conclusions about the effects of high frequency
wind variations at the field site, it is reasonable to expect that lower
frequency wind components are coherent over this distance. The six hour
averaging period used in Figure PO.II.4 was selected for clarity in
presentation of the data as well as to filter out the high frequency
part of the wind spectrum. Figure PO.II.4 shows that typically the
strongest winds are aligned within about 30° of north and south and have
Page 11
-------
magnitudes which range up to 15 m/s (34 mph).
Horizontal water velocity was measured at sampling point HRO (see
Fig. P0.II.1) from 4/4 - 4/21 using an Inter Oceans S4 current meter.
Measurements were made ~ 0.5 m above the bottom in a channel which was
~ 3 m wide and ~ 1 m deep below the top of the bank. Figure P0.II.5
shows vector plots of this data. Typical water movement in the upstream
or downstream direction occurred at speeds of 0 - 10 cm/s. Maximum
velocities reached 40 cm/s on 4/14 in the downstream rush of water
following the high water peak.
Salinity was measured in water samples taken hourly by three
automatic samplers, one of which collected surface water at point HRO
while the other two collected surface and bottom waters at point HR1.
The results for the period up until the automatic samplers were drowned
are presented in Figure P0.II.6. During this period the bottom water at
point HR1 maintained a near constant salinity of about 13 ppt while the
surface salinities at both points HR1 and HRO ranged from 1-13 ppt,
indicating that Home Road Creek varies from a stratified system to a
vertically well mixed system. The cause and importance of this are
discussed below.
Additional salinity measurements were made at daily intervals and
are presented in Table P0.II.1. It is interesting to note that the
water column at point HR2 at the mouth of Home Road Creek was seldom
more than weakly stratified even when strong stratification was present
at point HR1.
(ii) South Vest Creek Study, April 22 - May 9
Figure P0.II.2 indicates that one major rainfall occurred during
Page 12
-------
this interval, leaving about 40 mm of rain on 5/5. A moderate rainfall
of between 15 and 20-mm fell on 5/3 while smaller events occurred on
4/24 and 5/9.
Water level fluctuations measured at the mouth of the South West
Creek are shown in Figure P0.II.3. Variations during this period were
limited to a range of about 0.65 m and are more typical of the area than
those measured during the Home Road Creek study.
Wind velocity measurements in Figure P0.II.4 are similar in
character to those during the Home Road Creek study with strongest winds
typically aligned within about 30° of north and south and having
magnitudes which range up to 15 m/s (34 mph).
Horizontal water velocity was measured at sampling point SW1-A (see
Fig. P0.II.1) from 4/22 - 5/9 using an Inter Oceans S4 current meter.
The instrument was anchored ~ 1.5 m above the bottom in a cross section
approximately 6 m wide and 2.1 m deep below the top of the bank. Figure
P0.II.7 shows vector plots of this data. Typical water movement in the
upstream or downstream direction occurred at speeds of 0 - 10 cm/s.
Maximum downstream velocities of ~ 20 cm/s were measured on 5/5 and were
probably associated with runoff from rainfall falling earlier that day.
Salinity was measured in surface water samples taken every two
hours by automatic samplers located at SW1-B and SW0, Figure P0.II.8.
Surface salinities at point SW1-B typically ranged from 8-11 ppt while
those upstream at point SW0 typically ranged from 2-7 ppt.
Additional salinity measurements were made at selected intervals
and are presented in Table P0.II.1.
Page 13
-------
Discussion
It is well established that changes in waterlevel in Pamlico Sound
are predominantly wind forced. Due to the low relief of the surrounding
lands, these water level changes are easily propagated upstream and thus
can be expected to dominate the levels in rivers and creeks. A
comparison of Figures PO.II.3 and P0.II.4 illustrates this clearly.
Almost all decreases in water level are accompanied by southerly winds
(winds blowing from the south) which push water out of the southern end
of Pamlico Sound and the associated rivers, while almost all increases
in water level are associated with northerly winds. The extreme water
level recorded on 4/13 and 4/14 was the result of a prolonged period of
moderate northerly winds starting about 4/8 combined with 24-36 hours of
strong northerly winds, in excess of 10 m/s, on 4/13 and 4/14.
It is noted that since the water level in South West Creek is
dominated by the behavior of Pamlico Sound, it would be most appropriate
to have wind measurements over Pamlico Sound to describe the dominant
water level forcing. The close correspondence between Figures PO.II.3
and P0.II.4 provides some justification for the use of a 6-hour
averaging interval to filter out the spatially incoherent part of the
wind spectrum.
Estuaries are commonly separated into three categories based on
their vertical density structure: strongly stratified estuaries (often
called "salt wedge" estuaries), partially mixed estuaries and well mixed
estuaries. These are shown schematically in Figure P0.II.9. A strongly
stratified estuary is formed when the energy available for mixing is
insufficient to overcome the buoyancy of the fresh water discharge. A
well mixed estuary occurs when the mixing energy is" much higher than
Page 14
-------
the potential energy associated with the buoyancy of the fresh water
flow. Thus stratification is destroyed by strong mixing and enhanced by
a large fresh water discharge. Sources of mixing energy are bottom
friction, which is a function of the strength of the near bottom flow,
and wind stress, which depends on the wind speed and the surface area of
the water body.
Salinity measurements in Home Road Creek at points HRO and HR1
indicate that at least part of the time this water body is stronelv
stratified. This is despite the relatively low fresh water discharges
and is primarily due to the very small amount of energy available for
mixing. As the fresh water leaves Home Road Creek and enters South West
Creek, it spreads out laterally and, to conserve mass, must shrink in
depth. The decreased layer thickness along with the increased surface
area of South West Creek facilitate wind induced vertical mixing.
Therefore, it can be expected that the strength of the stratification
will decrease in South West Creek. This is consistent with the
measurements at HR2, most of which show little or no stratification.
Salinity measurements at HR1 indicate that this site was also
unstratified a significant portion of the time, having surface
salinities of 13 - 14 ppt. A comparison of the salinity data with the
water level data (Figure PO.II.IO) shows that significant increases in
surface salinity at HR1 are always associated with increases in water
level. This behavior occurs because the pressure gradient associated
with the rise in the water level of southern Pamlico Sound is stronger
than that associated with the fresh water outflow, causing unstratified
water from South West Creek to be forced back up into Home Road Creek.
(The PSWIKS data in Figures P0.I.6 and P0.I.7 illustrate this quite
Page 15
-------
clearly. After about 4:00 on 4/8 a rise in water level drives a
vertically uniform flow which pushes unstratified water past point HR1.)
This process is quite significant in effecting the impact of
agricultural runoff in Home Road Creek. During water level rises,
runoff is effectively trapped in the field ditches while during periods
of falling water level, its entry into the estuary is enhanced.
Chemicals entering Home Road Creek are confined to a thin fresh water
layer at the surface. If the water column biota penetrate this surface
layer they are exposed to high chemical concentrations. On the other
hand if they remain in the lower regions, most of the runoff passes them
by. Mixing in South Vest Creek provides a relatively large water mass
for the dilution of these chemicals (compared to the water column in
Home Road Creek). The biota in the lower part of the rater column do
not come in contact with the chemicals until a subsequent rising water
level pushes South West Creek water back up into Home Road Creek or the
density dirven circulation carries near bottom South West Creek water
into Home Road Creek.
Surface salinity measurements made at point SW1-B in the headwaters
of South West Creek are generally more constant that those measured in
Home Road Creek. While the salinity measurements at SWO reflect the
rainfalls of 4/24, 5/3 and 5/5, only the latter one significantly
affected the surface layer at SW1-B. Thus, with the exception of 5/6,
site SW1-B appears to be only weakly stratified. The salinity drop on
5/6 seems to be a combination of a large amount of fresh water runoff
from the previous day's rain and a rapid drop in water level at the end
of 5/5 (Figure PO.II.ll). During the following 48 hours the water level
gradually increases and eventually forces unstratified water back up
Page 16
-------
past point SW1-B on 5/7. The water level peaks near the end of 5/7 and
the following drop appears to allow another pulse of relatively fresh
(and perhaps high in chemical concentration) water to reach site SW1-B
on 5/8.
A major goal of the physical oceanographic component of project
ARIES is to quantify the flux of fresh water runoff into the estuary,
particularly following rainfalls which are strong enough to wash
agricultural chemicals from the fields. For typical density driven
estuarine circulation (Figure P0.II.9 ) the measurement of horizontal
velocity at one location in the vertical will provide little help in
accomplishing this since the velocity structure is not uniform over the
depth. During these times, velocities measured with the S4 current
meter at point HRO and SW1-A will be of little quantitative value.
During times in which the circulation is dominated by the pressure
gradient set up by water level changes in Pamlico Sound, the velocity
should be unidirectional over the depth. An example of this is the
period discussed above when unstratified South West Creek water was
forced upstream in Home Road Creek ori 4/8 (see Figure P0.I.6). During
much of the Home Road Creek Study and some of the South West Creek
study, a visual comparison of the horizontal velocities measured with
the S4 and the water level measurements does suggest that rises in water
level are usually accompanied by upstream velocities while drops in
water level are usually accompanied by downstream flow. Unfortunately,
we are still left without salinity profiles and therefore information
about the thickness of the fresh water runoff layer. Order of magnitude
calculations might be made using a typical fresh water layer thickness
shown in Table P0.II.1.
Page 17
-------
The instruments deployed with PSWIMS are ideally suited for the
purpose of determining fresh water flux in the estuary. Figure P0.II.12
shows the calculated fresh water and salt water fluxes/unit width for
part of 4/7 and 4/8. It is the objective of future PSWIMS deployments
to be able to make similar flux calculations during significant runoff
events.
Page 18
-------
vertical shaft
alignment
rail
bearing
collar
stainless
3teel wire
SLEEVE DETAIL
sleeve
k.
8 Delrin ball
bearings top
and bottom
shock cord
to lower pulley
single pulley-
N
traveling jsleeve
"I
Tattle Tale
DC Motor
»2 In dia. 1/4 In thick
PVC pipe
D
3 !rj dia. T fitting
double pulley
Figure rO.I.l. Principal components of PSWIHS
-------
1.00
0.75
WATER LEVEL MEASURED BY PSWIMS AT
HOME ROAD CREEK SITE 1
0.50
1 ' » ¦ '
1 '
16:00
20:00
0:00 4:00
TIME (hr)
8:00
15.00
12.00
9.00
6.00
3.00
SAUNITY MEASURED BY PSW1MS
0.76 METERS ABOVE BOTTOM
HOME ROAD CREEK SITE 1
0.00
I . .
* *
16:00
20:00
0:00 4:00
TIME (hr)
8:00
12:C
HORIZONTAL VELOCITY MEASURED BY PSWIMS 0.76 m ABOVE BOTTOM
o
o
EL
3
2.5 CX/S
16:00
20:00
4/6/88
0:00 4:00
TIME (hr)
8:00
4/7/88
12:0
Figure PO.I.3. PSWIMS data collected at Home Road Creek site 1 at a
fixed elevation 0.76 m above the bottom.
-------
1.50
LU
O
WATER DEPTH
.1.25
1.00
—Tide Guoge : Mouth of Southwest Creek
— Pswims : Home Rood Creek Site 1
0.75
16:00
20:00
4/7/8B
0:00
TIME (hr)
4:00
4/8/88
8:00
2.00
1.50
z.
2 1.00
I
LJ
0.50
0.00
PSWIMS VELOCITY AND SALINITY MEASUREMENT LOCATIONS
,»•••• •'•'•••I, '
.••••*• ••••~. * •••••*
>••••'•* #••••••
•••••••* *•••••••••
i«a«••*«
ft•••~
••••••
«•••••••• ••• • • •*
L
16:00
20:00
4/7/88
0:00
TIME (hr)
4:00
4/8/88
8:00
Figure PO.I.4. PSWIMS elevation measurements and sampling points
-------
SALMTY PROFILES MEASURED BY PSWIUS AT
HOME ROAD CRUX STIC 1
5.00 10.00 15.00
SAJJNTTY (ppt)
DOWWSTREAU WLOCJTY PROOLES UEASURED BY PSWWS
AT HOUE ROAD CREEX SHE 1
-4 -2 0 2 4 6 8 10
Op»lrtrom Doerurtreem N^lDCTTYjem/*)
CROSS STREAK \O_0QTY USEASyStHEHTS BY PSWWS
AT WOtAC ROAD CREEK SITE 1
1 ' 1 ¦—
•
[9 A
&
M
(KA.
1 . i »
4/7/88
O — 016-30-16:40
© — C 16:40—16:30 J
A— A 16:30-17:00 "
1 . 1 J.
-2
0 2 4
CROSS STREAM VODOTY (cm/i)
10
Figure P0.I.5. Sample salinity and velocity profiles measured by
PSWIMS
-------
LEVEL 7
Li
\V\l\i
tiz
ysl
7
LEVEL E
\1 .1 n\W
i rf i\'
y. '« j- y
M.\W,
77
I A ^
r mm > / i y
LEVEL 5
'\i'H l\i/iy' .
j »-
16:00
20:00
4/7
0:00
TIME (hr)
4:00
4/8
8:00
Figure PO.I.6. Vector plot of velocity data recorded by PSWIMS at Home
Road Creek site 1. The scale is 1 inch = 15 cm/s.
-------
SALINITY (ppt) MEASURED BY PSWIMS AT
HOWE CREEK SITE 1
TIME (hr)
4/7/88 4/8/88
Figure PO.1.7. Contour plot of salinity measured by PSWIMS. The
contour interval is 2 ppt.
-------
-------
100
80 -
AVERAGE RAINFALL AT OPEN GROUNDS FARM STUDY SITES
60 -
Z 40
h-i
<
QC
¦ n..
4/5 4/11 4/17 4/23 4/29 5/5
TIME (days)
Figure P0.II.2.
Rainfall recorded during the April/May study.
Rainfall from VI - 4/21 is an average from gauges at
RG1. RG2, RG3. RG4. Rainfall from 4/22 - 5/9 is an
average from gauges at sites RG1. RG2m. RG3. RG4.
-------
' 3/30 4/5 4/11 4/17 4/23 4/29 5/5
TIME (days)
Figure PO.II.3. Water level measurements during the April/May 1988
s tudy.
-------
6 HOUR AVERAGE WIND VELOCITIES MEASURED AT IMS
2.B H/8
| • 1 ¦ 1 ¦ 1 ¦ 1 * 1 ¦ 1 * 1 • 1 1 1 ¦ 1 1 1 ' 1 ' * ' * ' 1 ' * ' * ' * 1 * ' I ' ^
3/30 4/5 4/11 4/17 4/23 4/29 5/5
TIME (days)
Figure P0.II.4. Six hour averaged wind velocities recorded at the UNC
Institute of Marine Sciences during the April/May
study.
-------
APRIL 4-5
Is
3.CM/S
Mil. Al. . \ ¦ ViJv\ \\\ ,ll.
^V.ni'AV-wlV,
1^/71' 7/ljlf f"-
jilL
hlVj. h
APRIL 6-7
APRIL 10-11
> ¦ Q.»
1'/v/ij!firiii]Piyi|ir11 1 ijin /t
JkJv
APRIL 12-13
I < ' ' 1 » « ' t ' I I I I ' I 1 I I 1 I « ' » 1 1 ' I I ¦ I I I I I I 1 I » ' I I 1 1 I 1 I I t
0 4 a 12 16 SO 24 28 32 36 40 44 48
TIME (HOURS)
Figure PO.II.5. Vector plots of velocity data ~ 0.5 m above the bottom
at site HRO during the Home Road Creek study.. The
scale is 1 in. = 20 cm/s.
-------
Figure P0.II.5.
continued.
-------
Salinity at Home Road Creek Sites
HRO surface
HR1 surface
• • • HR1 bottom
i i
'6
4/7
4/8
4/9 4/10
Date
4/11
4/12
rigure P0.II.6. Salinity measurements taken from hourly water samples
during the Home Road Creek study.
-------
APRIL 22-23
I!
9 CX/S
^ /r ^ ^ ^ ^ jp">1 ^dtilJlfJ/j Xjjfl/
APRIL 24-25
-f/ -t.\V
/^/. ,f. h lllljf/rl. l.jf
APRIL 2&-2S
ml I/a ti
n r 4i
wr
APRIL 30 - KAY 1
Jhjll.jJ. jn!n mIi{w.
±j
11 HA'Yj'^l
i i > « i « i » i » t i i i i i i « t i i i i « i i i i i i i i i i » i i i » i i » . . i , , , t
0 4 B 12 16 20 24 28 32 36 40 44 48
TIME (HOURS)
Figure P0.II.7. Vector plots of velocity data ~ 1.5m above the bottom
at site SW1-A during the South West Creek study. The
scale is 1 in. = 20 cm/s.
-------
MAY 2-3
I
5 CX/S
MAY 4-5
i,^i!i$,f^jlj/t)l}$J\l/\/l/!lilll^l!*.jr,^>l\t}/j[/,s, ¦
KAY 6-7
KAY B-3
^,1 . f/ sMIy mIMiL
i^jk ., , \lflfy,
| | . . 1 t t t 1 « « « 1 i « i t » « « I i t i I i i i 1 i i I I 1 I I I I I I 1 * ' ' 1 I 1 ' I
0 4 a 12 16 20 24 28 32 36 40 44 4B
TIME (HOURS)
Figure P0.II.7. continued.
-------
Salinity at South West Creek Sites
— swo
- -SW1-B
/23
Figure PO.II.8. Salinity measurements taken from bl-hourly water
samples during the South West Creek study.
-------
STRONGLY STRATIFIED ESTUARY
water surface
Interfacg
0 7)
fresh water
flow
pr® rsur-e
dosnstrean
to. tarty
pressirr
up«-tr»an
PARTIALLY MIXED ESTUARY
WELL MIXED ESTUARY
water surface
^7
"D
pressur*
eJowrvstr^an
Ah
fresh water
f lo*
saltrtfty d«cr«asfr>B vtth
oks~tanc» fron the ocvan
pressure
liprtrvan
Figure PO.II.9. Estuarine classification scheme.
-------
18
1 6
14
12
10
>N
-4-J
C 8
• ¦«
"5
e/) 6
SALINITY AND WATERLEVEL AT HOME ROAD CREEK SITE
Q.
CL
1.5
Salinity HR1
Waterlevel
j \
1.0
c
o
o
>
Q)
0.5 lu
4
2
0
4/6 4/7 4/8 4/9 4/10 4/11 4/12
Date
0.0
Figure PO.II.IO. Comparison between surface salinity and water level
during the Home Road Creek study.
-------
SALINITY AND WATERLEVEL AT SOUTHWEST CREEK SITE
Salinity SW1-B
1 y/v
Waterlevel
r\
» / i r*
s V , 'H,/ w'
vl »> v
u V/'
i is
U\ V,i»/
\ A f,
\/
I » ' 1 I 1 L
1.5
1.0
- 0.5
0.0
4/23 4/25 4/27 4/29 5/1 5/3 5/5 5/7 5/9
Date
Figure PO.II.ll.
Comparison between surface salinity and water level
during l.h« South West Creek study.
-------
05
FLOW MEASUREMENTS BY PSWIMS
AT HOME ROAD CREEK SITE 1
in
• \m/ w
\
E
cr
cn
0.00
_c
i j
-a
"c
-.05
Z>
s
N
o
u_
-.10
a>
j j
¦? ~
~
£
~o
CO
-.15
V'
i
I \ , \ T i
11,1'1 'i
' "N
i i v i
r
i
i
— freshwater flux
saltwater flux
.01 ^
E
cr
in
0.00 ^
"O
5
.01 3
I!
5:
_o
u_
-.02 fe
o
_J I 1 I I I I J L I L
— .03
JZ
CO
-------
Table PO.II.l Additional Salinity data measured during April/May 1988
s tudy.
Depth
3-29-88
3-30-88
3-31-88
4-1-88
(cm)
HRO KR1 HR2
HRO HR1 HR2
HRO HR1 HR2
HRO KR1 HR2
surface
0. 0 2.6 9. a
0.5 2.0
0.0 0. 0 19. 0
1.0 1.0 9. 0
10
0.2 2.0 19.0
1.0 3. 0 12. 0
20
2. 0 12. 0 19. 0
6. 0 5.0 12. 0
30
4.5 19.0
9. 4 11.0 12. 2
40
7. 1 13. 0 19. 0
10. 5 12. 0 12. 8
50
6. '0 13.0
9.0 19.0
11.1 12.8 12.8
60
9.8 18.8
12.2 12.8 12.8
70
9. 8 13. 0 19. 0
12.5 12.6 12.8
80
19. 0
12.5 12.6 12.8
90
12. 6 12. 8
100
12.8 12.6
110
2. 2 13. 0 12. 2
9.8 13.0
13. 0
12. 5
Depth
4-2-88
4-3-88
4-4-88
4-5-88
( CTTl )
HRO HR1 KR2
HRO HR1 HR2
HRO HR1 HR2
HRO HR1 HR2
surface
1.2 1.5 12. 0
0. 5 1.0
0.0 0.8
1.5 5.0 7.8
10
1.5 3.0
1.5 2.0
0.2 2.0
3.6 13.0 12.3
20
7. 0 7. 5 12. 5
4.8 4.0
1.2 6. O
6.0 13.5 13.2
30
12.4 12.4
11.3 10. 0
4.2 9.0
9.5 13.5 13.2
40
12.6 12.8 12.7
11.9 11.0
6. 5 10. 1
10. 8
50
12. 6
12.1 11.0
7. 5 10. 4
11.5 13.5 13.2
60
12. 6
12. 1 11.0
10. 2 10. 6
12. 4
70
12.6 12.8 12.9
12. 2 11.0
10. 5 lO. 9
12.5 13.5 13.2
80
12. 6
12. 2
10. 9
12. 0
90
12.9 12.0
11.0
10. 9
13.5 12.0
100
12. 5
10. 8
10. 9
11. 8
110
12.7 12.2
13. 5
Depth
4-6-88
4-7-88
4-8-88
4-9-88
(cm)
HRO HR1 HR2
HRO HR1 HR2
HRO HR1 HR2
wf?-i HRO ran
surface
1.5 11.0
O. 4 1.5
6.8 6.4
2.0 6.2 13.4
10
3.0 12.2
1.2 3.5
13.2 13.4
2.0 6.4 13.4
20
3.5 12.6
1.3 11.2
13.4 13.4
4. 6 8. 4 13. 4
30
4.3 12.8
5.5 12.2
13. 4
8.0 13.2
40
6. 8
12.0 12.7
13. 4
9. 8 13. 2 13. 4
50
8.2 13.0
12. 0 13. 0
13. 4
60
9. 5
12. 2 13. 4
13. 4
10.4 13.4
70
10.5 13.0
12/3 13.4
13. 8
80
12. 3
12. 3 13. 5
13. 4
10. 6 13. 4 13. 6
90
12. 2
13. 6
100
13. 5
110
13. 2
13. 4
-------
Depth
4-10-88
4-n-aa
4-12-88
4-13-88
(cm)
HR-1 HRO HR1
(No Data)
HR-1 HRO HR1
'RUN-ON'!!!
surface
1.4 S. 8 12. a
10. 0 13. 2 12. a
10
1. 8 7.4 12.8
12. 2 15.0 13. 2
20
G. 0 1U2 12. a
13. 6 15. 0 13.2
30
10. 0 13. 2 12. a
13. 8 15. 0 13. 2
40
11.0 13. 4 13. 4
14.2 13.2
50
15. 0
£0
11.4 13. 6 13.2
14. 2 13. 2
70
15. 0
SO
11.4 13. 4 13. 2
14.2 13.2
90
14.8
100
14. 0
110
14.8 13.2
120
13. 2
130
14."S
140
13. 2
150
14. 4
-------
Depth
(cm)
ISO
200
SALINITY PROFILES - Home Road Creek Sites
(post 'Run-On'event)
4-14-68
KR-i HRO HR0.1 KR0,2 KR1 HR2 iy
). Q ±2.2
/
surface
6. a
7. 2
7. 2
S. 6
8. 8
10
6. 8
7. 4
8. 4
8. 6
a. 8
20
6. 8
7. 4
8. 4
8. 6
8. 8
30
7. 0
7. 6
8. 4
8. 6
9. 0
40
50
7. 0
7. 6
8. 6
8. 8
9. 0
60
70
7. 0
7. a
8. 8
8. 8
9. 8
60
9. 4
90
7. 2
8. 0
9. 4
10. 4
100
9. 8
110
7. 4
8. 6
9- 8
12. 2
120
130
9. 8
12. 8
140
8. 6
150
10. 2
10. 0
160
12. 8
170
10. 2
ISO
11.2
Depth
4-
15-88
( cm)
HR-1
HRO
HROJ.
KRCX2
HR1
HR2
D
surface
2. 4
3. 8
4. 0
4. 6
4. 6
7. 0
9. fa
10
2. 6
4. 2
4. O
4. 8
4. 6
7. 0
9. 8
20
2. 6
4. 4
4. 2
4. a
4. a
7. 6
9. 8
30
2. 6
4. 6
4. 0
5. 0
5. 0
11. 4
9. 8
40
4. 4
5. 2
6. 0
11. 6
SO
2. 8
4. a
4. 4
5. 4
6. 4
11. 6
11. 6
60
6. O
5. a
7. 0
11.6
70
2. 8
5. 2
6. 4
6. 8
8. 6
11.6
11.6
80
6. 6
7. 6
10. 2
11. 6
90
5. 8
8. 0
9. 4
11. 2
11. 6
11. 6
100
2. 8
5. a
10. 4
11. 6
11. 4
11. £
110
10. 6
11. 2
11. 6
11. 6
120
3. O
10. 0
11.2
11.6
11.8
10. 6
130
io. a
140
150
11.6
11.6
11.6
160
170
180
190
200
11.6
-------
:m )
f ac
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
210
SALINITY PROFILES - Home Road Creek
Post. 'Run-On' Sampling
4-16-88
KR-1 KRO HR01 HR02 HR1 HR2 . D
4-
HRO
19-88
:-:ri
1.0 5.6 8.4 9.6 10.4 11.0 11.6
1.0 5.8 lO. 6 10.2 11.4 11. 8 12.0
1.4 7.8 11.0 11.0 11.6 11.8 12.0
2.0 10.6 11.4 11.0 11.6 12.0 12.0
6. 0
7.8 11.6 11.4 11.4 11.8 11.8 12.0
7.2 11.6 11.6 11.6 11.8 11.6 12.0
11.6
7.8 11.6 11.6 11.6 11.8 11.4 12.0
11.6
11.6
11.6 11.6
11.4 12.O
3. 0
4. 0
4. 0
4. 0
4. 6
5. 0
6. 6
10. 0
10. 0
lO. O
10. 0
7. 0
7. 4
7. 6
7. 6
7. 8
11. 0
12. 2
12. 6
12. 8
12. a
12. 8
11. 8
11.8
-------
10
20
30
40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
200
SALINI7
4-14-88
SW1 SW2 SW
Y PROFILES - Southwest,
(post 'Run-On' event)
4-15-88
SW1 SW1A SW2 SW3
i.o 3. a a.
1.0 4.0 8.
1.0 4.0 8.
1. 4 4.6 8.
5. 0
1.8 5.8 9.
6. 8 9.
3.8 10.2 11.
1G. 2
3. 8 10.2
10.6 11.
3. 8
0
2
~2 i
10. 8
10.8 11.
8
10. 6 11. 0
0. 8
1. 0
1. 2
1. 2
i. 4
1. 8
2. O
2. 2
2. S
3. 8
3. 2
3. 4
3. 4
3. 6
5. 8
6. 6
6. 8
9. a
3. 4 11.0
5. 6 11. 2
7. 6 11.0
8. 8
9. 4
7. 4
7. 4
7. 0
7. 4
9. 8
9. 8
10. 4
10. 4
10. 4
10. 4
9. 0
9. O
9. 0
9. 0
9. 0
9. 2
9. 4
9. 4
9. 4
9. 6
9. 8
10. 4 10. 4
10. 4
10. 4
10. 0
10. 2
10. 2
10. 4
10. 4
10. 6
Creek
4-16-88
SW1 SW1A SW2 SW3
7. 8 10. 6 11.2 10. 8
8. 6 10. 6 11.4 11.0
9. 4 10. 8 11.4 11.0
10. 4 10. S 11.4 11.2
10.4 10.8 11.4 11.2
10. 6 11.0 11.4 11.4
11.0
10.8 11.4 11.6
10. 4
11. 4
11. 2
11. 0
10. 8
11. 6
ir. 4
11.2
-------
SALINITY PROFILES - Southwest Creek
Depth
4-22-88
4-23-88
4-25-88
4-27-88
( cm )
SWO SW1 SW1B
SWO SW1 SW1B
SWO SW1B
SWO SW1B
surface
2. 5 10. 2 8. 5
3.0 6.0 9.2
2. 2 9.8
2.0 6.0
10
3.0 10.2 8.5
3.0 6.0 9.2
3. 2 10. 2
2.2 8.0
20
3. 0 10. 2 9. 5
3.0 6.0 9.2
4.0 10.2
2.2 9.5
30
3. 0 10. 2 10. 0
3. 0 6. 0 9. 4
4.4 10.2
2. 5 10. 0
40
3. 5 10. 2 8. 0
6.0 9.4
10. 2
2.5 11.0
50
4. 0 10. 2 8.0
3.0 6.0 9.4
4. 0 10. 2
3. 0 11.0
60
5. 0 10. 2 8. 0
6.0 9.4
3. 2 11.0
70
5.5 8.5
3. 2
4.6 10.2
3. 6 11.0
80
5. 5 10. 2 9. 5
6.0 9.6
3. 8 11.0
90
4.0 11.0
100
6. 0 10. 2 9. 5
3. 2 6.0 9.6
4. 8
4.0 11.0
110
4.2 11.0
120
9. 5
9. 8
4.2 11.0
130
7. 0
6. 0
5. 4
4.2 11.0
140
11.0
150
i-*
o
UD
O
3.2 6.0
11.0
160
170
160
190
200
10. 4
200 +
Depth
4-29-88
5-1-88
5-3-88
5-5-88
( cm)
SWO SW1B
SWO SW1B
SWO SW1B
SWO SW1B
surface
0. 4 No
1.8 No
3. 4 No
1.4 10. 4
10
Data
Data
3.8 Data
1. 6
20
4. a
1. 6
30
5. 4
1. 6
40
50
5. 6
1. 8
£0
70
6. 2
2. 0
80
90
6. 6
lOO
110
6. 6
2. 4
120
130
140
150
160
170
ISO
190
200
200 +
< Bottom)
0. 4
9. 2
11.0
-------
SALINITY
Depth
5-6-88
(cm)
SWO SW1 SW13
surface
0. 0 0.0 2.0
10
0.0 0.0 2.4
20
0. 0 0.2 2.4
30
0. 0 0.4 10. 2
40
0. 6
50
0. 0 0. 6 11. 8
60
1. 0
70
0.0 7.4 12.0
80
9. 8
90
0. 0
100
110
9. 8
120
0. 0
130
140
150
12. 0
160
170
180
190
200
12. 0
200*
12. 0
< Eottora)
LES - Southwest Creek
5-9-88
SWO
SW1B
0. 2
5. 4
0. 2
9. 4
0. 2
11.2
0. 2
11. 4
0. 2
11.8
11.8
0. 2
12. 0
0. 4
12. 2
11. a
-------
1
BIOLOGICAL INVESTIGATIONS
Effects of Pesticides on the Mud Crab, Rhithropanopeus harrisii
In 1987 and 1988 three experiments were conducted using the common
estuarine mud crab, Rhithropanopeus harrisii, as the experimental animal.
Two of these were laboratory studies which, while not a direct part of this
project, were a result of our focus upon alachlor. The first experiment
was a laboratory study of the effects of the herbicide alachlor on larval
development (see attached reprint), the second was a study of effects of
alachlor on respiration of adult crabs (see attached preprint) and the
third involved rearing larvae from ovigerous females which had been held in
runoff from fields sprayed with the insecticide permethrin. The results of
the first laboratory study has been published, the second has been accepted
for publication and the third will be published in the Proceedings of the
National Pesticide Research Conference.
Exposure of Gravid Mud Crabs to Farm Water (2 phases)
In phase one, ovigerous crabs (Rhithropanopeus harrisii) with immature
eggs were held in farm runoff for 4 days at two sites. Site 3 (Home Road
Creek; Figure 1) received runoff for soybean fields while site 6 (Grassy
Knoll Creek; Figure 1) received runoff from mature corn fields. Crabs were
held in porous polyethylene containers filled with oyster shell which were
suspended in surface waters of the estuarine creeks by floats. Fields
draining into site 3 were sprayed with permethrin on August 22, 1987 at
89 ml/acre. On August 26 and again on August 31 approximately 2.5 cm of
rain fell but did not cause a runoff "event." On September 4 the ovigerous
crabs were placed at sites 3 and 6. On September 5-7 7.4 cm of rain fell
resulting in significant runoff from fields into the main canals.
Salinity at site 3 fell from 10 ppt to 0.5 ppt on September 5 and remained
below 3 ppt until crabs were brought into the laboratory on September 8.
The crabs returned to the laboratory were placed in clean 10 ppt sea water
for 4 days, at which time the eggs hatched (9/12). Ovigerous crabs and
larvae were maintained at 25°C under a 12:12 LD cycle. Fifty larvae from
each of 3 crabs from each site were then reared. Larvae were separated
into groups of 10 for rearing, thus there were 15 groups. Larvae were
reared for 96 h in 10 ppt to determine larval survival. Rearing procedures
consisted of placing larvae in clean water (10 ppt) each day, identifying
and discarding dead individuals, and then feeding live larvae newly hatched
Artemia sp. nauplii. After 96 h, larval survival in each group of 10 was
determined and a percent survival calculated. The results for all
15 groups in each condition were combined after arcsine transforming the
data and the mean standard deviation and standard error calculated. These
data were statistically compared to a control using a Dunnett test for
multiple comparisons with a mean. Control larvae came from crabs that were
not exposed to farm water but were reared using the same procedure. The
results were as follows:
-------
Fj
9UfQ
-------
3
Condition n Transformed Data Back Transformed Data
m SD m M+SE M-SE
Control 15 70.2% 15.7 88.6% 92.7 83.7
Site 3 15 72.7% 15.6 91.2% 94.7 86.8
Site 6 15 86.2% 10.9 99.5% 100 98.7
Analysis of results showed that larval survival after exposure at
sites 3 and 6 was not significantly lower than that in the control
conditions.
The phase two experiment consisted of exposing ovigerous crabs
collected at an uncontaminated site (Pine Cliff on the Neuse River) for
4 days to water from fields sprayed with permethrin and to uncontaminated
creek water and then rearing the larvae in these waters for 96 h. On
9/7/87 water (0 ppt) was collected from a ditch adjacent to the fields
(Block 64; Figure 1) which had been sprayed with permethrin (8/22/87) and
which had received 5.1-7.6 cm of rain on 9/6/87. Water (0 ppt) was also
collected from a forest stream which drains an undeveloped watershed
(Bridge Water). In both cases the salinity of the water was increased to
10 ppt by adding artificial sea salts. The procedures were as discussed
above and the control consisted of maintaining ovigerous crabs and rearing
larvae in clean 10 ppt. The results were as follows:
Condition n Transformed Data Back Transformed Data
m SD m +SE -SE
Control
15
67.6%
14.1
85.5%
89.7
80.8
Bridge water
20
78.1%
12.9
95.7%
97.5
93.5
Block 64
20
74.0%
13.9
92.4%
95.0
89.3
Analysis of results showed that in no case did exposure to Bridge or
Block 64 water significantly reduce survival compared with controls.
The results of the two phases of this experiment indicate that under
the conditions of the experiment (14 days between spraying and runoff)
there was no effect of runoff from permethrin-sprayed fields on mud crab
development.
The Grass Shrimp, Palaeomonetes pugio (Field Bioassays)
1987 Experiments
In August 1987 individual grass shrimp (Palaeomonetes pugio) were held
in cages in estuarine headwaters in a series of field bioassay experiments.
Three experiments were done in creeks (sites 3 and 4; Figure 1) receiving
-------
4
farm drainage from permethrin-sprayed soybean fields (Block 12; Figure 1)
and three experiments were done in a creek receiving only forest drainage
(Buck Creek; Figure 1). Thirty shrimp were held in experiments lasting two
to three days. Permethrin (approximately 30 /acre) was sprayed by air on
August 13 (Block 12). Based upon dye studies, runoff from these fields
could move to site 3 or site 4. Rainfall was 12 cm on August 10 and
8-10 cm on August 14. Experimental sites were visited daily between
10 a.m. and 1 p.m. and mortalities recorded. In addition temperature,
salinity and oxygen measurements were made. The results were as follows.
it
Live
# %
Dead Mortality
T(°C)
Sal. (ppt)
D.O. (ppm)
Control
Exp. 1 8/6-8/9
18
12
40
30.0
13.0 (12.1-13.7)
6.2 (2.9-11.8)
Exp. 2 8/10-8/13
11
16
59
28.0
8.3 (2.1-14.5)
4.8 (3.9-5.7)
Sep. 3 8/13-8/15
5
25
83
27.0
7.5 (2.1-15.2)
3.7 (3.2-3.9)
Runoff
Exp. 1 (Site 3)
8/6-8/9
29
1
3
29.4
7.1 (3.2-13.7)
3.8 (3.4-4.7)
Exp. 2 (Site 3)
8/10-8/12
0
30
100
27.0
3.3 (1.0-5.6)
7.4 (3.2-11.5)
Exp. 3 (Site 4)
8/12-8/14
0
30
100
24.1
1.6 (0.2-4.2)
4.0- (3.1-5.1)
Mortality in pre-runoff experiments was moderate (40%) in the control
site and low (3%) at the runoff site. Following a 13 cm rainfall on
August 10 but before permethrin spraying, mortality was 59% at the control
site and 100% at the experimental site receiving runoff. Following
permethrin application (August L3) and another rain (9 cm on August 14)
mortality rose to 83% in the control receiving forest runoff and was again
100% at the experimental site. These results suggested that significant
mortality was due to natural causes (low salinity and, perhaps, early
morning low oxygen) which would have masked any effects due to pesticide
inputs even if they had been present. Based upon these preliminary
bioassays, plans for 1988 included holding shrimp further downstream in the
estuary to keep salinities higher and placing cages so that there was
always an air/water interface to allow access to oxygen by caged animals.
1988 Experiments
In August and September 1988 gravid Palaeomonetes pugio were collected
and placed in plastic boxes with 1 mm nylon mesh. Boxes were placed in
wire cages with flotation attached to the sides to keep the. boxes at the
surface of the water to provide an air/water interface for each animal.
Twenty-five animals were held separately at each site for each experimental
period. Buck Creek and Doe Creek sites (Figure 1) received forest drainage
while Grassy Knoll Creek (Figure 1) received drainage from soybean fields
in farm Blocks 13 and 23. The animals were checked every two days and each
animal was recorded as being either alive or dead. Oxygen and salinity
measurements were taken each time the animals were-checked. Environmental
measurements and pesticide applications records were as follows:
-------
5
Environmental conditions and pesticide applications during field experiments during the
sunmer 1988. Sal=salinity (ppt); Oxy=oxygen (ppm) for spraying T=thiocarb,
P=permethrin, B=faim block # draining into Grassy Knoll Creek and F=field ditch //.
Date
Rain
Grassy Knoll Cr.
Doe Creek
Buck Creek
Pesticides
(cm)
Sal
Qxy
Sal
Qxy
Sal
Qxy
8/23
16.0
7.1
16.5
3.6
T(B23; Fl^)
8/24
3.6
8.8
6.3
15.4
2.6
8/25
8.2
3.5
8/26
6.0
4.7
12.4
2.5
T(B13,F3-5; B23, F-7)
P(B13,F6-8)
8/27
13.5
8/28
0.5
12.0
5.6
18.0
3.5
8/30
12.0
5.2
17.5
4.1
8/31
3.0
10.0
9/1
13.8
7.9
18.0
7.2
9/2
0.8
9.0
9/3
2.0
5.4
9.0
7.2
T(B13,Fl-2; B23, F9-12)
9/4
2.8
15.5
9/5
12.2
7.2
6.0
6.4
9/7
0.5
13.4
7.9
18.4
5.2
9/8
P(B13,F9)
9/9
0.3
9/10
1.3
9/12
10.0
10.8
During the first experiment (8/23-8/28) both thiocarb and permethrin
were applied to fields in the drainage area. Rainfall of 3.6 cm on 8/24,
which occurred prior to permethrin spraying, caused salinity to decrease
from 16 ppt to 6 ppt at the treated site (Grassy Knoll Creek) but only
caused a slight reduction at the untreated site (Doe Creek). Permethrin
was applied on 8/26 but since salinities increased through 8/28 it appears
that little or no runoff reached the caged animals. There were no deaths
at either the treated or untreated sites.
The location of the untreated site was changed to Buck Creek in the
second experiment because oxygen values were consistently low at Doe Creek
during experiment 1. During the second experiment (9/2-9/7) additional
thiocarb was applied to fields located in the treated drainage system on
9/3. Changes in water level in the South River estuary on 9/3 resulted in
salinity decreasing from 13.8 on 9/1 to 2 ppt on 9/3 probably subjecting
the animals to runoff water from the 8/24 and 8/31 events which would have
transported permethrin into the estuary if it was present in the runoff
(analysis of water samples for permethrin is underway). Salinity at the
treated site increased again to 15.5 on 9/4 and then decreased again
slightly following a 2.8 cm rain. Salinity at the untreated site (Buck
Creek) decreased from 18 ppt to 6 ppt and then returned to 18 ppt during
the experiment. There was no mortality grass shrimp noted at either site.
Two of the twenty-five shrimp were missing at each site, presumably having
escaped from the cages.
-------
6
Effects of Alachlor on Marine Phytoplankton
Two species of marine algae (Prorocentrum micans and Skeletonema
costatum) were the subject of preliminary experiments to examine the
effects of alachlor on growth rates of populations of these phytoplankters.
These projects were done by students for Independent Study course credit at
the Duke University Marine Laboratory under the direction of W. Kirby-Smith
and R. Forward. Abstracts of the results are presented below.
K. Condict. Alachlor acute toxicity tests using Prorocentrum micans
A dinoflagellate representative of phytoplankton of the South River
estuary, Prorocentrum micans, was grown in cultures exposed to the
following concentrations of alachlor: control, 0.1 ppm, 1.0 ppm, 10 ppm and
50 ppm. The mean growth rate in controls was 0.36 divisions/day.
Significant (P=0.05) inhibition of growth occurred at alachlor
concentrations of > 1.0 ppm. Probit analysis yielded a 120-h EC,^ value of
1.9 ppm. Chlorophyll a per cell was greater than controls at 0.1 ppm
alachlor, not significantly different at 1 ppm and 10 ppm and significantly
decreased at 50 ppm.
A.S. Home. The effects of the herbicide alachlor on growth of the diatom
Skeletonema costatum.
Skeletonema costatum was grown in cultures exposed to the following
concentrations of alachlor: control, 0.001 ppm, 0.01 ppm, 0.1 ppm and
1.0 ppm. Concentration of 1.0 ppm alachlor reduced growth rates by 73%
compared to controls and 65% to acetone controls. Chlorophyll a_ per cell
and chain length of populations exposed to alachlor were no different from
controls.
Nektonic Communities
Fall 1987
Fish communities were sampled by standard N.C. Division of Marine
Fisheries trawl (two minute/137 m) weekly from mid-September through
October, 1987. Six small creeks or embayments (Figure 1) were sampled on
each of 7 sampling dates. Four creeks received forest drainage (Big
Creek #1, Eastman, Doe and Buck) while two received farm drainage (Big
Creek // and Southwest). Fish collected were identified, counted, weighed
and measured.
During the fall eleven fish species were collected (Table 1). Three
species were dominant (99.6% by number): bay anchovy (Anchoa mitchilli) ,
spot (Leiostomus xanthurus) and mullet (Mugil cephalus) while seven were
dominant in biomass (96.4%): bay anchovy (A. mitchilli), spot
(L. xanthurus), striped mullet (M. cephalus) , pinfish (Lagodon rhomboides) ,
croaker (Micropogonias undulatus), southern flounder (Paralichthys
lethostigma), and Atlantic menhaden (Brevoortia tyrannus). Numbers and
biomass (Table 2) of fish remained relatively high until late October when
the predictable fall decrease took place.
-------
Table 1. Total number and total biomass (in grams)
of each fish species encountered. For each species,
all sites at all sample dates were combined (6 sites
with 7 trawls lasting 2 min).
Species
Total
Total
Number
Biomass (g)
Bay Anchovy
13,787
2645
Spot
100
2254
Striped Mullet
65
1103
Pinfish
15
663
Croaker
14
716
Southern Flounder
10
317
Yellowfin Menhaden
8
373
Hogchoker
7
100
Silver Perch
4
115
Naked Goby
4
0.8
Ladyfish
1
85
Table 2. Total number and total biomass
(in grams) for each sample date. All
species for all sites are combined
(6 sites; 2-min trawl at each site).
Date Total Total
Number Biomass (g)
9/17
3692
1292
9/24
2528
1278
10/2
2117
1929
10/8
1557
1349
10/15
2697
1105
10/22
614
750
10/29
816
658
-------
8
A comparison of forest with farm creeks indicated: (1) No significant
differences in total catch, either number or biomass (Table 3); (2) No
significant differences in number on any one date (Table 4); and (3) No
Table 3. Total number, total biomass means
and standard deviations of fish caught in
the two creek types, t-test results for
number and biomass between creek types.
Neither t-test is significant.
FOREST RUNOFF
FARM RUNOFF
t-TEST
II
c
n=2
TOTAL NUMBER
X=2616
X=1775
t=l.102
s=996.96
s=1352.70
df=4, n.s.
TOTAL BIOMASS (g)
X=1227.7
X=1740.8
t=l.719
s=401.03
s=43.44
df=4, n.s.
Table 4. Total number (of all species) means and
standard deviations between creek types for each sample
date. T-tests show no significance for any sample
date.
DATE
FOREST RUNOFF
FARM RUNOFF
t-TEST
9/17
X=776
X=295
t=0.637
s=996.96
s=249.61
df=4, n.s.
9/24
X=513
X=239
t=l.241
s=251.02
s=76.37
df=4, n.s.
10/2
X=201
X=658
t=0.916
s=159.88
s=696.50
df=2, n.s.
10/8
X=243
X=292
t=0.274
s=220.21
s=158.39
df=4, n.s.
10/15
X=460
X=428
t=0.086
s=424.28
s=438.41
df=4, n.s.
10/22
X=118
X=71
t=0.288
s=210.12
s=95.46
df=4, n.s.
10/29
X=45
X=318
t=0.906
s=40.63
s=424.97
df=2, n.s.
-------
9
significant difference in biomass on any one date except October 15 when
significantly greater biomass was caught in the farm runoff creeks
(Table 5). Cluster analysis to assess community similarities indicated no
difference in fish communities among the creeks. Hydrographic data
collected on each sampling date indicated no predictable differences in
water temperature, salinity, dissolved oxygen or secchi depth. Water
temperature decreased from approximately 28° in early September to 16° in
late October. Salinity varied from 12 ppt to 17 ppt and dissolved 0„
values ranged from 3 to 9 ppm. Secchi depths increased as fall progressed
with a range of 15 cm to 40 cm on 9/17 to 110 cm to 160 cm on 10/29.
Rainfall was relatively light during the sample period probably resulted in
only slight runoff during the period.
Table 5. Total biomass (of all fish species) means and
standard deviations between creek types for each sample
date. * significant p > 0.05.
DATE
FOREST RUNOFF
FARM RUNOFF
t-TEST
9/17
X=232.1
X
II
t—'
00
r*o
o
t=0.222
s=283.08
s=l76.42
df=4, n.s.
9/24
X=235.0
X=169.1
t=0.586
s=125.49
s=142.41
df=4, n.s.
10/2
X=244.2
X=476.1
t=2.068
s=97.44
s=196.44
df=4, n.s.
10/8
X=208.6
X=263.1
*t=3.689
s=19.29
s=6.86
df=4, s
10/15
X=134.1
X=284.4
t=1.771
s=47.83
s=177.61
df=4, n.s.
10/22
X=82 .0
X=210.9
t=l.062
s=75.54
s=247.91
df=4, n.s.
10/29
X=86.7
X=155.3
t=0.859
s-101.97
s=53.15
df=4, n.s.
Summer 1988
Fish communities in the upper South River were sampled by trawl on
9 occasions July through August 1988. Three replicate, one-minute trawls
were taken in six creeks; three which received farm runoff and three which
received forest runoff. Fish and shrimp were identified, counted, and
weighed (wet). Trawling was done using a standard N.C. Division of Marine
Fisheries nursery stock assessment trawl. The two-seam otter trawl had a
3.2 m headrope with 6.4 mm bar mesh wings and body and 3.2 mm bar mesh
tailbag. Each trawl was 1 minute in duration and covered a distance of
-------
10
2
67.5±8.5 m distance. The trawls swept an average area of 216 m . Farm and
forest drainage creeks (Figure 1) were paired by proximity to each other
and physical attributes. Elishu (farm) paired with Buck (forest),
Southwest (farm) with Eastman (forest), and Royal (farm) with Little
(forest).
The total catch data for the summer of 1988 (Table 6) show a community
typical for upper estuarine creeks of the Pamlico Sound region. Most
abundant by number were Bay Anchovy (Menidia menidia) which are a primary
forage species food for larger predatory fish. The nursery function of
these systems is demonstrated by the catch of juvenile spot, croaker,
flounder, and shrimp. Spot were second in numbers to Bay Anchovy but were
dominated by weight. Pinfish and Silverperch, also forage species, made up
the remainder of the more abundant fish species. Penaeid shrimp (Penaeus
spp. - mostly £. aztecus) were also present in moderate abundance, ranking
4th in number and 5th in weight.
Total catch by date (Table 7) showed a general increase in both number
and biomass as the summer progressed. Although rainfall was moderate
throughout the period, salinities remained high (15-18 pp) in surface
waters measured at the time each collection was made. The 7/25 trawls were
taken to see if a 6.4 cm rainfall (7/22-7/23) influenced catches. There
was a drop in number and biomass however salinities did not decrease
significantly. Rapid decreases in salinity or oxygen are known to cause
temporary emigration of nekton from small estuarine creeks.
The total catches from each of the creeks is shown in Table 8. There
were no patterns in the data based upon land use. One forest creek
(Eastman) had lowest total number and biomass while another forest creek
(Little) had highest numbers and biomass. In comparing paired creeks there
were two cases (Elishu/Buck and Royal/ Little) in which farm creeks had
somewhat lower numbers and biomass than forest creeks but the third pair
(Southwest/Eastman) had the opposite pattern. These data illustrate one of
the possible pitfalls in field research in which only one replicate
"experimental" and "control" system is compared (pseudoreplication) for any
specific attribute.
There were no predictable patterns in number and biomass when the data
are summarized by creek on each date (Table 9). The catch from all creeks
except Eastman did decrease following rain (compare 7/21 to 7/25) but there
were other similar variations in comparing other dates.
The data summarizing the distribution of total catch by species
relative to location are presented in Table 10. One farm drainage creek
(Elishu) stood out as having an extremely low abundance of Bay Anchovy
compared to other creeks. However abundance of other species (Spot,
Croaker, Pinfish, shrimp) in Elishu was no different from other creeks.
Another farm creek (Royal) had the greatest number of Bay Anchovy, more
than twice the number of all creeks except Elishu. In addition Royal had
the greatest number of species of any of the other creeks.
-------
11
Table 6. Total catch from three replicate trawls
at six locations on nine dates from upper South
River tributaries during the summer 1988.
Species Number Biomass (g)
1.
Anchovy
23,288
5029
2.
Spot
3,038
21829
3.
Croaker
327
3158
4.
Pinfish
177
2635
5.
Flounder
32
357
6.
Hogchoker
18
100
7.
Silver Perch
33
80
8.
Menhaden
14
98
9.
American Eel
9
346
10.
Naked Goby
6
0
11.
Pipefish
1
1
12.
Bluefish
3
19
13.
Lizardfish
2
128
14.
Silverside
33
56
15.
Brown Shrimp
200
2054
Table 7. Total fish catch by
date. Data are the sum of three
replicate trawls at six locations
on each date.
Date Number Biomass
(8)
7/1/88
969
5189
7/7/88
725
43459
7/14/88
1808
3906
7/21/88
3003
4574
7/25/88
2291
2429
7/28/88
4150
3123
8/4/88
4557
2926
8/12/88
2996
3425
8/25/88
6682
5973
Table 8. Total fish catch by
location. Data are sum of three
replicate trawls at each site on nine
dates.
Station Number Biomass
(g)
Elishu 1251 6021
Southwest 1791 9948
Royal 1305 6046
Buck 1575 9289
Eastman 630 2511
Little 2169 12888
-------
12
Table 9. Total catch from 3 replicates at each location on each sample
date.
Date
Station
Number
Biomass
(g)
Date
Station
Number
Biomass
(g)
7/1/88
Elishu
139
669
7/28/88
Elishu
82
715
Southwest
199
1105
Southwest
51
174
Royal
145
672
Royal
1857
718
Buck
175
1032
Buck
632
499
Eastman
70
279
Eastman
1268
327
Little
241
1432
Little
260
690
7/7/88
Elishu
66
403
8/4/88
Elishu
86
571
Southwest
91
294
Southwest
1316
421
Royal
166
1159
Royal
1121
492
Buck
118
722
Buck
623
415
Eastman
57
354
Eastman
912
404
Little
227
1412
Little
499
623
7/14/88
Elishu
58
439
8/12/88
Elishu
305
995
Southwest
353
330
Southwest
24
158
Royal
1013
1200
Royal
1220
1091
Buck
80
540
Buck
47
144
Eastman
88
362
Eastman
33
287
Little
216
1035
Little
1367
750
7/21/88
Elishu
123
675
8/25/88
Elishu
172
1343
Southwest
435
489
Southwest
1860
611
Royal
- 1389
993
Royal
3248
1897
Buck
286
1012
Buck
100
780
Eastman
457
426
Eastman
119
224
Little
313
979
Little
1183
1117
7/25/88
Elishu
41
287
Southwest
239
314
Royal
478
296
Buck
138
493
Eastman
1020
396
Little
375
642
-------
13
Table 10. Total number of individuals of each species (Table 1) caught in
three replicate trawls from nine dates from each creek. H'=diversity
Creek H' Species
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Elishu
3.71
375
573
65
15
6
5
0
0
6
0
0
0
0
3
24
Southwest
1.20
4133
384
32
6
0
0
0
2
0
0
0
1
0
0
10
Royal
1.20
9844
493
114
46
11
11
24
8
1
1
0
0
1
7
76
Buck
2.73
1560
522
44
31
6
1
6
1
2
0
0
0
0
0
26
Eastman
1.07
3719
250
32
1
1
1
0
2
0
1
1
2
1
0
13
Little
2.34
3657
816
40
78
8
0
3
1
0
4
0
0
0
23
51
Diversity (H1) was greatest (3.71) in a farm drainage creek (Elishu)
because of the greater evenness of the number of individuals due to the low
numbers of anchovies. Buck and Little, forest drainage creeks, had the
second and third greatest diversity (2.73 and 2.34 respectively). Although
Royal, a farm creek, had the greatest number of species (13) its diversity
was relatively low due to the high dominance by Bay Anchovy, lowest
diversity (1.07) was seen in Eastman, a forest drainage creek.
Throughout the estuarine systems catches of Bay Anchovy increased
through time as did the number of species (Table 11). Spot remained
relatively constant in abundance while croaker, shrimp and flounder
decreased in abundance over the summer. Diversity decreased dramatically
from a high of 3.20 on 7/7 to a low of 0.77 on 8/4 as Bay Anchovy abundance
increased together with a decline in abundance of some of the other
species.
Nektonic community similarities were compared using 3 sets of data
based on species abundance (numbers) (Figure 2). In the first set the
three replicate trawls at any one time and place were added together and
treated as one sample, giving a total of 54 communities (six locations and
nine dates). There were only two major groups which were distinct in
comparisons among 54 communities. Group 1 contained those communities
which had relatively low numbers of Bay Anchovy while Group 2 had high
numbers. In the second analysis, data from the 9 dates were added together
for each station to see if there were patterns of community structure
related to location. Adding these data together in this fashion reduced
the variability in catches such that all locations except Elishu Creek
cluster tightly together as a single community type. Elishu differed in
having very low abundance of Bay Anchovy. Finally, in the third analysis,
when collections were lumped together by date there appeared to be a
temporal pattern in community structure with 7/1 and 7/7 forming one group
(Group 2), and all others forming a second group (Group 1). The 7/14
community appeared to serve as a link between the two groups. Again the
difference was primarily related to the number of Bay Anchovies, with the
increase in abundance as time progressed causing the two distinct community
types.
-------
Cluster Analysis of Fish Communities
SIMILARITY
fJtntinn /Dntfl 0.2 0.0
/ ' I I I I I I I I I I
E1.L2.M8-
B1.E2
S1.R1.M2.B9
R2.E3
L1
M1,S2,B2.B3.L3|
E5,E6,E7,S8,E9 f
E4
L4.B5.S6.L6.B8.E8
M3
GROUP 1
S3.R4.M4.R5.M5.R6
B6.M6.S7.R7.B7.M7 i—i
L7.R8.L8.S9.R9.L9 M
R3.S4.B4.S5.L5.M9 —*
GROUP 2
Stations:E=Elishu,M=Eastman,L=Little.B=Buck,S=Southwest.R=Royal
Dates: 1=7/1.2=7/7.3=7/14.4® 7/21.5-7/25
6—7/28,7=8/4,8=8/12,9=8/25
BUCK (Fo)
EASTMAN (Fo) -
LITTLE (Fo) —
SOUTHWEST (Fa)
ROYAL (Fa) —
EUSHU (Fa)
GROUP 1
GROUP 2
Fo=FOREST, Fa=FARM
7/21
7/25
7.28
8/4
8/12
8/25
7/14
7/1
7/7
GROUP 1
GROUP 2
Figure 2. Community analysis of nekton collected in the summer
-------
15
Table 11. Total number of individuals of each species (Table 1) caught in
three replicate trawls from six locations on the date given. H'=diversity
Date
H'
Species
7 8 9 10 11 12 13 14 15
7/1
3.19
92
711
62
60
7
0
0
0
0
0
0
0
0
0
37
7/7
3.20
76
532
43
31
4
1
0
0
0
0
0
1
0
0
37
7/14
2.76
1310
385
43
16
4
4
1
2
0
3
0
0
1
0
39
7/21
1.97
2571
273
60
20
7
5
25
2
2
0
0
0
0
0
38
7/25
1.50
2041
182
36
14
3
1
1
2
1
1
1
0
0
0
8
7/28
1.00
3891
179
33
14
3
1
4
4
0
1
0
0
0
0
20
8/4
0.77
4328
191
13
6
1
1
2
0
0
0
0
0
0
0
15
8/12
1.18
2731
225
23
3
2
3
0
0
3
0
0
0
0
0
6
8/25
0.96
6248
360
14
13
1
2
0
4
3
1
0
2
1
33
0
In summary there were no patterns in fish communities which could be
attributed to location with reference to farm versus forest drainage.
Communities were more or less identical to those found at similar locations
throughout the Pamlico Sound System. No large fluctuations in salinity
were observed during the period in spite of the normal to moderate
rainfall. It is well known that if there is displacement of the salt
water/freshwater interface in shallow estuaries marine fish migrate to
higher salinities but then return with the return of saltier water. Based
on these data it is apparent that the farm activities have not caused a
permanent change in the nekton community in creeks receiving runoff as
compared to creeks in forested watershed. During the summer of 1989 nekton
sampling will shift from bottom to surface trawls in the same set of creeks
to assess surface nekton community which may be more quickly displaced as
salinity of surface water decreases during rainfall events.
Benthic Communities
Benthic communities were sampled 5 times during the summer 1988 (July-
September) at approximately 2-week intervals. Six replicate core samples
were taken at each of six tributary creeks of the South River (3 farm
runoff, 3 forest runoff) on each sampling date. These creeks were the same
as sampled for nekton. The top 10 cm on each of each core was preserved in
the field with 10% formalin and stained with Rose Bengal. In the
laboratory samples were sieved (0.5 mm) and all organisms sorted from
debris. Bivalves were not sorted from the first two sets of samples but
were sorted thereafter. Species were identified and counted.
In analysis, the six replicates were summed for each creek and each
date. Cluster analysis to determine community similarity was done using
pooled data (all dates) for each station. Analysis has been completed for
the first three of the five sampling dates.
Samples (Table 12) were dominated by the -polychaetes Mediomastus
californiensis, Streblospio benedicti, the oligochaete Peloscolex sp., the
bivalve Macoma tenta and the mysid shrimp Mysidopsis bigelowi. Forest and
-------
16
Table 12. Total species abundance of benthic animals
collected from six replicate cores taken on three separate
dates (18 samples) for each forest and farm creek (BU=Buck,
EM=Eastman, LT=Little, EL=Elishu, SW=Southwest, RY=Royal).
Forest
Farm
1
2
3
4
5
6
BU
EM
LT
EL
SW
RY
Mediomaster
59
47
200
81
26
250
Peloscolox
36
26
49
60
12
123
Stroblospio
38
50
62
22
29
41
Macoma tenta
11
10
5
12
12
19
Mysidopsis
17
6
13
16
18
10
Heteormastus
4
5
12
10
-
25
Nereis
16
9
8
16
1
5
Insect L
2
14
9
1
3
21
Melinna
4
1
7
1
-
10
Eulalia
2
-
4
3
5
5
Gyathura
1
2
6
5
-
1
Scyphiatoma
-
-
2
4
6
-
Novertina
-
-
4
2
-
3
Macomba B
1
3
1
1
1
1
Gammarus
-
-
6
1
-
-
Lethoscolopis
-
-
1
-
-
5
Edotea
1
1
1
-
1
-
Rangia
-
3
-
-
-
-
Syllidae
-
-
-
-
-
2
Spiosetosa
-
-
1
-
-
-
Corophium
—
—
1
—
it Species
13
13
19
15
11
15
i Individuals
192
177
392
235
115
521
H'
2.77
2.84
2.50
2.78
2.83
2.38
farm creeks differed little in the communities of benthic invertebrates.
The greatest number of species (19) were found at Little Creek (forest
runoff) with two farm runoff creeks (Royal and Elishu) second having
15 species each. Fewest species (11) were found in Southwest Creek which
received farm runoff. The greatest density of animals (521) was found in
Royal and least (115) at Southwest, both farm runoff creeks). Diversities
were moderate and similar in all creeks ranging from a low of 2.38 at Royal
Creek to a high of 2.84 in Eastman Creek. In cluster analysis all the
creeks came together at a 0.91 similarity indicating no significant
differences among them in community structure.
-------
17
In summary there were no differences in benthic communities which
could be correlated with differences in type of drainage, forest or farm.
Furthermore the species present and the moderate diversity of these creeks
make them very similar to other small creeks found in areas of low to
moderate salinities throughout the Pamlico Sound system.
-------
Experiment 1
Estuaries Vol. 11, No. 2. p. 79-82 June 1988
Effects of the Herbicide Alachlor on
Larval Development of the Mud Crab,
Rhithropanopeus harrisii (Gould)
Richard L. Takacs
Richard B. Forward, Jr.
William Kirby-Smith
Duke University Marine Laboratory
Beaufort, North Carolina 28516
ABSTRACT: The effects of the herbicide alachlor, in both technical grade and commercial product form (Lasso),
were tested for acute toxicity on larvae of the estuarine crab Rhithropanopeus harritii. The generalized effect is a
reduction in survival and a lengthening of developmental time with an increase in concentration. The LC„ values
were inversely proportional to exposure time and ranged from 10 to 27 mg 1"'. Lasso was slightly more toxic than
technical grade alachlor.
Introduction
Alachlor [2-chloro-2'-6'-diethyl-N-(methoxy-
methyl)acetanilide] is the active ingredient (45.1%)
in Lasso, a widely used herbicide produced by the
Monsanto Agricultural Products Company. The
herbicide is used primarily with corn and soybean
crops as a preemergent inhibitor of annual grasses,
broadleaf weeds, and yellow nutsedge (Monsanto
1984).
Due to its high rate of application (1.68-4.48 kg
ha-1), high solubility in water (242 mg 1~') and high
stability, alachlor is persistent in soil and aquatic
environments (Weed Science Society of America
1979). Detectable levels of alachlor can persist in
soils for up to one year and in farm drainage water
for up to four weeks (Skaggs et al. 1980). Because
of these characteristics, alachlor can readily leach
through soils during heavy rainfall. Although most
concentrations of alachlor range between 0.078
and 0.184 mg 1"' in drainage streams (Wauchope
1978), Skaggs et al. (1980) found levels in farm
ditch water as high as 2.7 mg 1"' immediately fol-
lowing a runoff event.
Much of the coastal plain wetlands that have been
converted to agriculture border directly on eco-
logically sensitive and economically important es-
tuarine water systems. These systems are suscep-
tible to direct runoff from wetlands agriculture. In
recent years, the fates and effects of herbicides and
pesticides once they enter the aquatic ecosystem
has been of great concern, but little lethal or sub-
lethal toxicity data exist with direct estuarine ap-
plicability.
Larvae from the crab Rhithropanopeus harrisii
were chosen for study because (1) this species is an
abundant animal in low salinity headwaters of es-
tuaries, (2) the technique for larval rearing is well
known (Costlow et al. 1966), (3) the larval stages
are typically the most sensitive to environmental
variables (Thorson 1964), and (4) R. harrisii larvae
have been shown to be sensitive to various pollu-
tants (e.g., Christiansen and Costlow 1975; For-
ward and Costlow 1978; Bookhout et al. 1980).
In this paper toxicity tests and analysis for post-
hatch exposure are described for both Lasso ala-
chlor and technical grade alachlor.
Methods and Materials
Preparation of Toxicant and Dilutions
Lasso, an emulsifiable concentrate (EC) of ala-
chlor, was obtained commercially, while the tech-
nical grade alachlor was supplied in crystalline form
by the Monsanto Agricultural Products Co., St.
Louis, Missouri. For experiments on the effects of
alachlor, a stock solution was made from each form
of alachlor. Ten ml of Lasso EC alachlor (480 g
1"') was pipetted into a glass 1 1 bottle and allowed
to evaporate. Certified A.C.S. acetone was then
added to give a final volume of 480 ml stock so-
lution, which produced a nominal concentration
of 10 mg ml-1 (10,000 mg l"1). Stock solution of
the technical grade alachlor crystal was created by
dissolving 3 g of the crystal in 300 ml of acetone,
for a stock solution of 10 mg ml"1. Stock solutions
were stored in the dark at 5 °C and were replaced
after each 30-day period.
Standard dilution techniques were used for both
solutions. Acetone serial dilutions of 2,500, 1,250,
500, 50, and 5.mg I"1 were made daily. To each
7-cm diameter glass finger bowl, 1 ml of dilution
© 1988 Estuarine Research Federation
79
0160-8347/88/020079-04S01 50/0
-------
80
R. L. Takaes et al.
Fig. 1. The percent of larvae developing to the megalopa
stage plotted against concentration (mg 1"') of Monsanto ala-
chlor (A) and Lasso (B). Means and standard errors are shown.
The n for each determination was 15. Acetone and seawater
indicate the percent survival in the acetone and seawater control
solutions. The asterisk indicates mean percent development is
significantly (p < 0.05) different from the seawater control.
was pipetted and allowed to evaporate in a hood.
The remaining alachlor film was then resuspended
in 50 ml of filtered (5 ^m) seawater (salinity 20%o)
to give final alachlor concentrations of 50, 25, 10,
1, and 0.1 mg I-1. Acetone controls and seawater
controls were also tested. Acetone controls were
set up by pipetting 1 ml of acetone into each test
bowl and allowing it to evaporate. This was de-
signed to reveal any possible effects of an acetone
residue following evaporation on the test bowls.
The additional control was to expose larvae to fil-
tered (5 nm) seawater (20%o).
All glassware to be used in herbicide toxicity tests
was first washed in a 10% HC1 bath, and then
washed in a concentrated (37 N) H2S04 bath, fol-
lowed by a deionized water rinse and a final acetone
rinse. Subsequent daily washes consisted of scrub-
bing bowls with a clean brush in deionized water,
followed by an acetone rinse. Separate bowls were
used at each concentration throughout the exper-
iment to reduce the risk of cross contamination
among concentrations.
Rearing of Larvae
Ovigerous females of Rhithropanopeus harrisii
(Gould) were collected from the Neuse River in
North Carolina. Females were held individually in
an environmental chamber in large (19 cm diam-
eter) finger bowls containing 20%o filtered (5 fim)
seawater. Chamber temperature remained at 25 °C
(±1 °C), and a 12:12 LD cycle was maintained.
Hatching normally occurred 2-3 h after the dark
phase began (Forward et al. 1982).
Upon hatching, the adult female was removed
from the bowl, and larvae were fed newly hatched
Artemia sp. nauplii. Larvae of R. harrisii were also
reared under the same environmental conditions
as above (20%o; 25 °C; and a 12:12 LD cycle). These
parameters have been shown to be optimum con-
ditions for laboratory rearing and development in
R. harrisii larvae (Costlow et al. 1966).
Approximately 12 h after hatching, larvae from
each of three hatches (minimum hatch size: 400
larvae) were placed in the test solution. Five rep-
licates of 10 larvae from each hatch were tested in
each solution. Thus the total number of replicates
for each condition was 15. Dilution and control
solutions were renewed daily, and larvae were fed
newly hatched Artemia sp. nauplii. Dead larvae and
molts were counted and removed at this time.
Toxicity Experiments
Three experimental series were conducted. First,
the chronic tests consisted of continuously expos-
ing larvae to the test solution throughout larval
development. Effects were evaluated as percent
survival at the megalopa stage and time duration
to reach this stage. Both technical alachlor and
Lasso were tested.
In the second experiment larvae were exposed
to test solutions continuously for 96 h beginning
just after hatching. Survival after this time was
recorded. This experiment used both technical
alachlor and Lasso and was designed to determine
the 96-h mean lethal concentration (LC50)-
Finally, the third experiment involved short-term
exposure and was designed to test the effect of a
simulated short duration runoff event. Larvae were
exposed to test solutions of Lasso for 12 h just after
hatching during the light phase and then trans-
ferred to clean seawater. Mortality was measured
after 96 h.
For data analysis, mean percent survival and the
standard errors were calculated after arcsine trans-
formation of the data. Since all experiments con-
sisted of a control and many test concentrations,
differences were tested using a Dunnett t test for
multiple comparisons with a control (Dunnett
1964). The LC50 values were determined by probit
analysis.
Results
Chronic Exposure to Monsanto
Alachlor and Lasso
When exposed to 25 and 50 mg I"1 of Monsanto
alachlor (Fig. 1A), no larvae completed develop-
ment to the megalopa stage. At concentrations of
1 and 10 mg I"1, survival was significantly lower
than in seawater alone; whereas, at 0.1 mg 1"' and
in the acetone control, survival was similar to that
in seawater (Fig. 1A). The LC50 level was 14 mg
1"'. For larvae that survived, the duration of larval
-------
Herbiicide Effects on Crab Larval Development
81
Monsanto alochlor
l0?
'2 -j B Lasso
-h
IO
Concentration
Fig. 2. The number of days for development from stage I
zoea to megalopa plotted against concentration (mg l_1) of Mon-
santo alachlor (A) and Lasso (B). Mean and standard error times
are shown and the average n was 14 in A and 1 1 in B. Seawater
and acetone indicate developmental times in these control so-
lutions. Double asterisks indicate development time is signifi-
cantly (p < 0.01) longer than in seawater.
development to the megalopa stage increased with
Monsanto alachlor concentration and was signifi-
cantly longer than that in seawater at 10 mg l"1
(Fig. 2A).
Similar results were obtained with Lasso. No lar-
vae survived at 25 and 50 mg l"1, and the lowest
test concentration to significantly reduce survival
was 10 mg l"1 (Fig. IB). Survival in all other test
conditions was not significantly different from levels
in seawater. The LC50 was 10 mg 1"'. The length
of larval development increased as survival de-
creased and was significantly longer at 10 mg 1_1
(Fig. 2B).
Fig. 3. The percent of larvae surviving for 96 h after ex-
posure to various concentrations (mg h1) of Monsanto alachlor
(A) and Lasso (B). Means and standard errors are plotted. The
n for each determination was 15. Seawater and acetone indicate
the percent survival in these control solutions. The single and
double asterisks indicate survival was significantly lower than
levels in the seawater control at the p < 0.05 and 0.01 levels,
respectively.
Fig. 4 The percentage of larvae surviving after 12-h ex-
posure to various concentrations (mg I"') of Lasso. Means and
standard errors are plotted and the n for each concentration
was 15. Seawater and acetone indicate percent survival in these
control solutions. Double asterisks show those concentrations
at which the percent survival is significantly lower than that in
the seawater control at the p < 0.01 level.
Acute Exposure for 96 h to
Monsanto Alachlor and Lasso
Exposing larvae to the herbicide for the first 96
h of development also caused a significant reduc-
tion in survival. In Monsanto alachlor significant
effects were seen at 25 and 50 mg l"1 (Fig. 3A).
The LC50 was 26 mg 1"'. Larvae were more sen-
sitive to Lasso, the lowest concentration to signif-
icantly lower survivorship was 10 mg I"1 (Fig. 3B).
The Lasso LC50 occurred at 16 mg 1~\ a lower
concentration than alachlor.
Acute Exposure for 12 h to Lasso
As larvae were more sensitive to short-term ex-
posure to Lasso (Fig. 3B), larvae were exposed to
various concentrations for 12 h and then placed in
clean seawater. Mortality was determined after a
total time of 96 h. Larval survival was significantly
reduced at concentrations of 25 mg l"1 and greater
(Fig. 4). The LC50 was 27 mg M.
Discussion
The generalized effect of alachlor on Rhithro-
panopeus harrisu larvae is a reduction in survival
and a lengthening of developmental time with an
increase in concentration. Sensitivity was inversely
proportional to exposure time; the estimated LC50
concentrations decreased as exposure time in-
creased (Table 1).
The usefulness of larval crustaceans as test or-
ganisms for pollutants entering estuarine systems
TABLE 1. The estimated LC50 values upon exposure to Mon-
santo alachlor and Lasso for various time periods.
LC„
Monsjnto
alachlor
Lasso
Exposure Time
mg 1"
mg 1"'
Continuous (Fig. 1)
14
10
96 h (Fig. 3)
26
16
'2 h (Fig. 4)
—
27
-------
82 R. L. Takacs et al.
has been discussed in detail by Epifanio(1979). The
planktonic larval stages of crustaceans are consid-
ered the most sensitive to environmental pertur-
bations in the life cycle (Thorson 1964). That lar-
val crustaceans usually are much more sensitive to
pesticides than adults has been dramatically illus-
trated by Wilson (1985), who found that grass
shrimp (Palaemonetes pugio) had a 96-h LC50 for
diflubenzuron (an insect growth regulator) of 1.4
ng 1"' as larvae, 1.6 ng l-1 as postlarvae, 202 ng l"1
as males and nonovigerous females, and 6,985 as
ovigerous females.
The LC50 concentrations for R. harrisii larvae
range from 10 to 27 mg l-1 alachlor (Table 1).
These values are similar to those for an adult non-
marine crustacean (crayfish), where the LC50 for
alachlor was 19.5 mg l"1 (Weed Science Society of
America 1979). The LC50 concentrations, how-
ever, vary with the type of alachlor tested. Lasso
EC alachlor, with its inert detergent carriers, is
slightly more toxic (lower LC50 values) to R. harrisii
larvae than technical grade Monsanto alachlor (Ta-
ble 1). This result is in partial agreement with past
studies. Acute dermal LD50 studies on rabbits show
Lasso to be more toxic than technical grade ala-
chlor (Weed Science Society of America 1979).
However, freshwater fish (bluegill, sunfish, trout)
were more sensitive to technical grade alachlor than
Lasso.
In field studies the alachlor concentration in
water of ditches draining a coastal plains farm in
North Carolina peaked at times of peak flow and
usually ranged up to approximately 0.07 mg l_l
(Skaggs et al. 1980). These concentrations are well
below those causing mortality in crab larvae. How-
ever, on several occasions Skaggs et al. (1980) re-
ported concentrations up to 2.7 mg l~l, values much
closer to LC50 levels. Although there were no data
available, they suggested that these concentrations
may have resulted from wind drift spray falling
directly into the ditches. Thus there is the possi-
bility of rare-to-occasional short-term exposure to
significant concentrations of alachlor by crab lar-
vae in upper estuarine creeks which receive direct
drainage from farms. The 12-h pulse experiments
simulated a heavy runoff event where concentra-
tions of the herbicide would be at high levels for
a short period of time. R. harrisii adults inhabit low
salinity areas in creeks, thus they are in a position
to be exposed to undiluted runoff water. Since ear-
ly stage larvae are sensitive to short-term exposure
(12 h), reproductive success could be affected by
alachlor.
Even though the present study indicates R. har-
risii larvae are sensitive to alachlor, it is possible
that even greater sensitivity exists during embryo
development. Thus future experiments will con-
sider what effect exposing the eggs to alachlor has
on future larval survival. In addition, sublethal ef-
fects on larval behavior should be investigated as
these might indicate ecological effects which could
influence the crabs at concentrations well below
that necessary to produce direct mortality.
Acknowledgments
This study was supported by the National Science Founda-
tion's Research Experience for Undergraduates (to RLT) and
funded in part by Environmental Protection Agency Contract
#CR 813415-01. We thank Dr. D. Rittschof and A. Schmidt
for designing the dilution techniques and laboratory assistance
of C. Sommers. We also thank Open Grounds Farm, Inc. for
supplying the Lasso and Monsanto Agricultural Products, Inc.
for providing the technical grade alachlor.
Literature Cited
Bookhout, C. G., J. D. Costlow, JR., AND R. Monroe. 1980.
Kepone effects on larval development of mud crab and blue
crab. Water Air Soil Pollul 13:58-77.
Christiansen, M. E., andJ. D Costlow, jr 1975. The effect
of salinity and cyclic temperature on the larval development
of the mud crab Rhitliropanopeus harrisii reared in the labo-
ratory. Mar. Biol. 32:215-221.
Costlow,J. D.,jr., C. G. Bookhout, and R.J. Monroe. 1966.
Studies on the larval development of the crab, Rhithropano-
peus harrisii (Gould). I. The effect of salinity and temperature
on larval development. Physiol. Zool. 39:81-100.
Dunnett, C. W. 1964. New tables for multiple comparisons
with a control. Biometrics 20:282-291.
Epifanio, C. E. 1979. Larval decapods (Arthropoda- Crusta-
cea: Decapoda), pp. 259-292. In C. W. Harl, Jr. and S. L. H.
Fuller (eds.), Pollution Ecology of Estuarine Invertebrates.
Academic Press, New York.
Forward, R. B , jr., and J D. Costlow, jr. 1978. Sublethal
effects of insect growth regulators upon crab larval behavior.
Water Air Soil Pollut. 9:227-238.
Forward, R. B , jr.. K. Lohman. and T. W Cronin. 1982.
Rhythms in larval release by an estuarine crab {Rhithropano-
peus harrisii). Biol Bull. 163:287-300.
Monsanto Company. 1984. Lasso: Herbicide by Monsanto—
Complete Directions for Use. St. Louis, Missouri. 16 p.
Skagcs, R. W., J. W. Gilliam, T. J. Sheets, and J. S. Barnes.
1980. Effect of agricultural land development on drainage
waters in the North Carolina tidewater region. Water Resour.
Res. Inst., Univ. North Carolina. Rep. #159. 164 p.
Thorson, G. 1964. Light as an ecological factor in the dis-
persal and settlement of larvae of marine bottom inverte-
brates. Ophelia 1:167-208.
WauchOpe, R. D. 1978. The pesticide content of surface water
draining from agricultural fields—A review. J Environ Qual.
7:458-472.
Weed Science Society of America. 1979. Herbicide Hand-
book, 4th ed., Weed Science Society of America, Champaign,
Illinois. 479 p.
Wilson, J. E. H. 1985. Sublethal effects of diflubenzuron (Di-
milin) on the reproduction and photobehavior of the grass
shrimp Palaemonetes pugio Holthuis (Caridea, Palaemomdae).
Ph.D. Thesis, Duke University, Durham, North Carolina
21 1 p.
Received for consideration, December 7, 1981
Accepted for publication, March 15, 1988
-------
Respiration and osmoregulation of the estuarine crab
Rhithropanopeus harrisii (Gould): Effects of the herbicide alachlor
David W. Diamond, Laura K. Scott,
Richard B. Forward, Jr. and W. Kirby-Smith
Duke University Marine Laboratory
Beaufort, NC 28516 USA
919/728-2111
Running title: Herbicide effects on crab respiration and osmoregulation
-------
Abstract
1. The effects of a sudden decrease in salinity and exposure to sublethal
concentrations of the herbicide Alachlor on osmoregulation and
respiration of the crab Rhithropanopeus harrisii were studied.
2. Crabs were hyperosmotic regulators at salinities below 24 ppt and
became hypoosmotic at higher salinities. Upon a salinity decrease
from 20 to 1 ppt, crabs adjusted their haemolymph osmolality to a
stable hyperosmotic level in 8 h. Alachlor concentrations to 50 ppm
did not affect this adjustment.
3. A salinity decrease from 10 to 0 ppt elevated V0~ and the critical
oxygen tension. This response was unaffected by Alachlor
concentrations as high as 25 ppm.
-------
Introduction
The crab Rhithropanopeus harrisii is perhaps the most abundant crab in
the upper reaches of estuaries along the southeastern United States
(Williams, 1984). Runoff from agricultural lands following rainfall can
lead to a rapid decrease in salinity in estuarine areas and exposure to
products used in agriculture. The present study was initiated because
large numbers (unquantified) of dead R. harrisii were found following
runoff from an agricultural area that was recently treated with the
herbicide alachlor. Although many environmental factors could contribute
to crab death, exposure to alachlor and a salinity decrease were chosen for
study.
The herbicide alachlor (2-chloro-2'-6ldiethyl-N-(methoxymethyl)
acetanilide) is the active ingredient (45.1%) in Lasso produced by the
Monsanto Agricultural Products Company (Monsanto, 1984). It is used as a
preemergent inhibitor of annual grasses, broadleaf weeds and yellow
nutsedge with corn and soybean crops.
Alachlor is very soluble in water (242 ppm) and is widely used in
amounts of 1.68 - 4.48 kg/ha by the farming industry (Weed Sci. Soc. Amer.,
1979). Previous research has found that alachlor can remain in the soils
for up to 1 year (Skaggs ej: al. , 1980). After heavy rainfall alachlor can
easily be leached from soils into drainage systems, which transport it to
estuaries. Concentrations of alachlor in drainage waters have been
measured at 0.078 to 2.7 ppm (Wauchope, 1978; Skaggs et^ al^. , 1980).
A recent study of alachlor effects on larval development of an
estuarine crab, Rhithropanopeus harrisii, found that there was a reduction
in survival and a lengthening of developmental time with an increase in
concentration (Takacs e£ al., 1988). Lasso was slightly more toxic than
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2
technical grade alachlor, and the values ranged from 10 to 27 ppm
depending upon the exposure time. Effects were evident after as little as
12 h exposure. Since these values exceed the upper levels measured in
nature and adults usually have higher levels than larvae, adult
_R. harrisii will probably be exposed to sublethal levels of alachlor in
nature. Osmoregulation ana respiration represent two physiological
processes that could be affected by sublethal stress, and if altered, could
contribute to an animal's death.
Osmoregulation is well studied among crustaceans (recently reviewed by
Gilles and Pequeux, 1983). Using inorganic ion concentration as a measure
of the relationship between hemolymph and seawater osmolality, Smith (1967)
suggested that R. harrisii was a hyperosmotic osmoregulator at salinities
between 1 and 23 ppt but became hypoosmotic at higher salinities. The
present study determined this relationship by directly measuring seawater
and haemolymph osmolality and considered the effects of alachlor upon
acclimation to a sudden reduction in salinity.
Respiration is also well studied in crustaceans (recently reviewed by
Cameron and Mangum, 1983; Vernberg, 1983). In estuaries, the oxygen
concentration fluctuates widely throughout the 24 h day, being highest
during mid to late afternoon as a result of photosynthesis and being least
at late night and early morning due to the combined respiration of aquatic
plants and animals (e.g. Warner, 1977; Kenney et: al. , 1988). When the
external oxygen tension is high many crustaceans exhibit independent weight
specific oxygen consumption rates (VQ2) and when external oxygen tension is
low, dependent V ^ occurs. The inflection oxygen tension for the switch
from independent to dependent respiration is the critical oxygen tension
(P : Hill, 1976). Both and the P were used as an assay for the
c 02 c
-------
3
effects of alachlor and salinity decrease upon respiration of R. harrisii.
Results indicate that neither osmoregulation nor respiration were affected
by sublethal concentrations of alachlor.
Materials and Methods
Rhithropanopeus harrisii (Gould) were collected without regard for sex
or molt stage from the Neuse River, North Carolina from September to
November. They were kept unfed in 10 ppt seawater in glass finger bowls
(19 cm diameter) at a temperature of about 23°C. The water in the bowls
was changed every two days, and all experiments were completed within
3 weeks of collection.
Herbicide preparation
Lasso , an emulsifiable concentrate (EC) of alachlor, was obtained
commercially and used in the experiments because this form is slightly more
toxic than pure alachlor to R. harrisii larvae (Takacs ejt al^ , 1988) and it
is the form to which crabs are exposed in nature. A stock solution was
made by pipetting 10 ml of Lasso EC alachlor (480 g/L) into a 1 L glass
bottle and allowed to evaporate. Certified A.C.S. acetone was then added
to give a final volume of 480 ml stock solution, which produced a nominal
concentration of 10 mg/ml (10,000 ppm). The stock solution was stored in
dark at 5°C. Unless otherwise specified in the remaining paper, the
£
designation alachlor is derived from Lasso .
Standard dilution techniques were used to produce acetone dilutions of
2500 mg/L (ppm), 1250 ppm and 500 ppm. To each 7 cm diameter glass finger
bowl, 1 ml of dilution was pipetted and allowed to evaporate to dryness in
a hood. The remaining alachlor film was then 'resuspended in 50 ml of
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4
filtered (5 ym) seawater at the test salinity to give final alachlor
nominal concentrations of 10, 25 and 50 ppm. These concentrations were
used because the LCj.q values for _R. harrisii larvae with identical
techniques ranged from 10 to 27 ppm. (Takacs e_t al_. , 1988) , these values are
sublethal for the adults and these values are the same order of magnitude
as the highest levels reported in nature (Skaggs et al., 1980). Test crabs
remained alive upon exposure to test concentrations of alachlor. An
acetone control was not run because larval development was not affected by
acetone (Takacs et al., 1988).
Osmoregulation experiments
An initial experiment determined the relationship between haemolymph
osmolality and external salinity. Groups of five crabs were acclimated for
one week to separate salinities ranging from 1 to 30 ppt at 4-5 ppt
intervals. The different salinities were made up by mixing dechlorinated
tap water with seawater and were measured with a refractometer (A.O.).
Approximately 10 yl of haemolymph was withdrawn from the base of the crab's
walking legs using a 1 cc syringe with a No. 27 needle. Haemolymph
osmolality was measured immediately with a vapor pressure osmometer
(Wescor, Inc., Model 5100B). The osmolalities of the acclimation waters
were measured with the same osmometer.
To determine the rate of acclimation of haemolymph osmolality upon a
sudden salinity change, crabs were acclimated for 3 days to 20 ppt and then
placed in I ppt. These salinities were used because the crabs are
approximately isosmotic at 20 ppt (Fig. 1) and a decrease to 0-1 ppt is a
realistic salinity level after a heavy rain in estuarine areas inhabited by
the crabs. The exact procedure was to acclimate 21- crabs to 20 ppt. Blcod
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5
osmolality was initially determined for 3 crabs. The remaining crabs were
then transferred into 1 ppt seawater and 3 crabs were sampled thereafter at
1, 4, 8, 12, 24 and 48 h.
The tests for the effects of alachlor upon osmoregulation consisted of
acclimating 18 crabs to 20 ppt for 3 days. Two separate groups of 3 crabs
were initially sampled to indicate haemolymph osmolality upon acclimation
to 20 ppt. Two groups of 6 crabs were then placed individually in separate
finger bowls containing 50 ml of 25 ppm or 50 ppm alachlor made up in 1 ppt
seawater. Haemolymph of three crabs was sampled at 12 and 24 h. These
times were selected because acclimation occurs within 8 h and alachlor
effects on larvae are evident after 12 h exposure time (Takacs et al.,
1988).
Respiration experiments
Since R. harrisii is a small crab (average adult weight about 0.4 g)
and the water volume of the respirometer flasks was relatively large, it
was necessary to measure oxygen uptake for groups of crabs. For each
trial, seven crabs of approximately equal size were placed in a clean
bottle filled with air saturated seawater (approximate volume = 350 ml). A
fiberglass screen was inserted into the bottle for the animals to hold onto
during the trial. The bottle was then sealed with a self-stirring oxygen
probe. This apparatus was placed in a water bath maintaining a temperature
of 24.5°C. Crabs were allowed to settle for 15 min, after which
measurements of the oxygen concentration in the water were made every
15 min using an oxygen meter (Model 54, Yellow Springs Instruments Co.,
Inc.) attached to the bottle probe. The trial was terminated when the
meter reading remained unchanged for 1 h. The oxygen concentrations at
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6
each measurement interval throughout the test period were then converted to
weight specific oxygen consumption rate anc* t*ie average oxygen
tension for each 15 min interval.
To study the effects of salinity on respiration, 4 trials were
initially run for separate groups of crabs acclimated for 1 week to 10 ppt.
The study of the effect of a salinity decrease upon respiration used the
same procedure, except that the oxygen consumption of the crabs was
determined 24 h after placement in 0 ppt water. This time was selected
because crabs completed osmotic acclimation to a salinity decrease within
24 h (Fig. 2).
Two experiments examined the effects of prior exposure to alachlor and
a sudden decrease in salinity upon respiration. First animals were
acclimated to 10 ppt seawater for at least one week and then exposed to 10
or 25 ppm alachlor for 24 h. Crabs were then placed in herbicide-free
10 ppt seawater for 0.5 h, and respiration subsequently tested in 10 ppt
seawater. Testing in herbicide-free water reduced contamination of the
respiratory equipment. Second, crabs were acclimated to 10 ppt for at
least one week and then placed in 0 ppt water containing 25 ppm alachlor
for 24 h. Crabs were then placed in herbicide-free 0 ppt water for 0.5 h
after which respiration was measured in another volume of herbicide-free
0 ppt water.
Each experiment was replicated two or four times and all data were
used to plot Vq2 at the various oxygen tensions because the crabs were all
of approximately equal weight. A computer-derived 5th order polynomial
best fit curve was drawn to approximate the respiratory rate as the oxygen
tension decreased. Trials with different equations indicated this
polynomial provided the best fit to the data. For.each set of trials, the
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7
average for the independent respiration was calculated between oxygen
tensions of 50 and 100 mm Hg. This interval eliminated the initial
elevated values caused by handling and disturbance of the animals when
first placed in the bottle and also eliminated the possibility of including
low V values during dependent respiration, because the critical oxygen
tension (P ) was below 50 mm Hg for these crabs. This average V line was
C U 2.
also plotted on the graph. A vertical line was drawn from the point at
which the best fit curve fell below the average line to determine the
P value,
c
Results
Osmoregulation experiments
R. harrisii were acclimated to salinities ranging from 1 to 30 ppt.
Haemolymph osmolality remained hyperosmotic until about 24 ppt (Fig. 1) and
became hypoosmotic at higher salinities.
Crabs acclimated relatively rapidly upon a salinity decrease from
20 to 1 ppt (Fig. 2). Haemolymph osmolality decreased gradually for the
first 8 h -and then stabilized around 550 mOsm. Mean haemolymph
osmolalities at S h and longer were not significantly different (Student t
test) from the mean value upon acclimation for 1 week at 1 ppm (Fig. 1).
The test for the effect of alachlor on osmoregulatjon indicated that
neither 25 nor 50 ppm affected this process (Fig. 3). When the salinity
decreased from 20 to 1 ppt in the presence of alachlor, the haemolymph
osmolality decreased and stabilized at about the same level as it did when
alachlor was not present (Fig. 2). Since j*. harrisii is a strong
hyperosmotic regulator (Fig. 2), a decline in the level of hyperosmotic
regulation was predicted if osmoregulation was affected.
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8
Respiration experiments
The respiratory pattern was the same under all test conditions
(Figs. 4-8). At high oxygen tensions there was a very high V^n) which
probably resulted from an initial increase in activity upon being placed in
the respirometer bottle. At progressively lower oxygen tension levels, the
crabs displayed independent respiration followed by dependent respiration.
At control conditions of 10 ppt and no alachlor, the average was
102.8 ul C^/s/h, and the crabs switched to dependent respiration at
15.9 mm Hg (Fig. 4; Table 1). Prior exposure of alachlor in 1C ppt
seawater caused an increase in the V ^ and (Figs. 5,6; Table 1).
Upon a salinity decrease from 10 to C ppt both the V and were
elevated (Fig. 7) as compared to respiration in 10 ppt. However, when
subjected to this salinity decrease in the presence of 25 ppm alachlor,
similar and ?c values were observed (Fig. 8; Table 1). Thus alachlor
did not have anv additional effect on the respiratory change upon a
decrease in salinity.
Discussion
A pattern of hyperosmotic regulation at low salinities and hypoosmotic
regulation at high salinities is typical of estuarine grapsoid crabs
(Barnes, 1967) and species living in high intertidal areas (Jones, 1941).
However, most subtidal estuarine crustaceans are hyperosmotic at low
salinity and become isosmotic at high salinities (e.g. Callinectes sapidus,
Ballard and Abbott, 1969; Panopeus herbstii, Blasco and Forward, 1988).
In salinities ranging from 1 to about 24 ppt, R. harrisii is an
osmcregulator, remaining hyperosmotic to the external environment. At
salinities greater than about 24 ppt, the crabs, displayed hypoosmotic
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9
regulation. These results agree with the previous study by Smith (1967).
His measurements of haemolymph CI concentration suggested that _R. harrisii
was a hyperosmotic regulator at salinities from 1 to 23 ppt and perhaps a
hypoosmotic regulator at higher salinities.
JR. harrisii acclimated its haemolymph osmolality to a decrease in
salinity within 8 h. This relatively rapid rate of adjustment is similar
to that observed for a related species Panopeus herbstii (Blasco and
Forward, 1988), which stabilized its haemolymph osmolality within 4 h upon
an 8 ppt decrease in salinity. However most crustaceans require 12 to 24 h
to stabilize their osmolality (C. sapidus, Tagatz, 1971; Engel and Nichols,
1977; Callianassa jamaicense, Felder, 1978). Neither 25 ppm nor 50 ppm
alachlor affected the rate or level of adjustment by R. harrisii upon a
dramatic salinity change from 20 ppt to 1 ppt.
Upon exposure to declining oxygen tensions, R. harrisii shows the
pattern of independent respiration at high tensions which changes to
dependent respiration at low tensions. This pattern is typical of many
crustaceans (Mangum and Van Winkle, 1973), especially those living in an
environment having variable oxygen tensions.
Under possible normal conditions in an estuary (10 ppt,
0 ppm alachlor), Rhithropanopeus harrisii has a P£ of 15.9 mm Hg (Table 1)
and is in no danger of tissue damage caused by insufficient oxygen because
normally the minimum measured oxygen tensions that occur in estuarine
creeks in the summer at night are approximately 25 mm Hg (unpublished data,
W. Kirby-Smith). The animals probably never switch to dependent
respiration under normal salinities and thus their blood is always
saturated with oxygen and no stress is caused to their tissues (Redmond,
1955). Under conditions of heavy rainfall in herDicxde-free runoff creeks,
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10
however, the salinity may decrease to about 0 ppt, which causes the to
increase to approximately 24 mm Hg and the average V ^ to increase by about
30%. This increase in respiration may represent the energy needed for
increased hyperosmotic regulation. In this situation the respiratory
volume and cardiac output may not saturate the blood to keep up with the
elevated oxygen demands of the body, and the organism may experience
anaerobic damage resulting in death (Arudpragasam and Naylor, 1964; Taylor
and Butler, 1973; Taylor, 1976; Warner, 1977).
When exposed to both 10 ppm and 25 ppm alachlor in 10 ppt seawater,
both the V „ and P are elevated, which indicates the animals are
02 c
experiencing sublethal stress. However, this situation is unrealistic
because exposure to alachlor will be accompanied by a salinity decrease due
to rain water runoff. Under conditions of 25 ppm alachlor and a salinity
decrease, the average and P^ increase by about 30% and 50%,
respectively. This increase in and V ^ must be caused by the
hypoosmotic stress because the and P£ values are very similar to those
upon a salinity decrease alcne (Table 1). If the reduction in salinity
occurs at night when there is no photosynthetic activity, the dissolved
oxygen concentration may decline below the new critical oxygen tension and
dependent respiration may result. If animals are prevented from reaching
the air/water interface, or if they are unable to switch to anaerobic
respiration for a long enough duration, then the animals may be stressed
past their limits. This situation may explain the observed deaths of
R. harrisii, which prompted this study.
Runoff events expose estuarine animals to low salinity water, which
can potentially contain high concentrations of herbicides. Respiration and
osmoregulation of adult _R. harrisii are affected- by rapid decreases in
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11
salinity but alachlor did not affect hyperosmotic regulation or elevate
respiration beyond the level due to the salinity decrease alone. Test
concentrations of alachlor were at or above the levels for larvae
(Takacs e£ a_l. , 1988) and the same order of magnitude of the highest levels
found in drainage areas (Skaggs ££ al., 1980). Thus it is unJikely that
alachlor caused the observed death of R. harrisii in the field after a
runoff event which prompted this study. A more likely explanation is that
death resulted from elevated respiration in response to the salinity
reduction and reduced oxygen levels at night (Kenney et al., 1988).
Acknowledgements
This study was funded in part by Environmental Protection Agency
Contract #CR 813415-01. We thank Monsanto Agricultural Products, Inc. for
providing the technical grade alachlor.
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12
Literature Cited
Aruripragasam K. D. ana Naylor E. (1964) Gill ventilation volumes, oxygen
consumption and respiratory rhythms in Carcinus maenas (L). J. Exd.
Biol, 41, 309-321.
Ballard B. S. and Abbott W. (1969) Osmotic accommodation in Callinectes
sapidus (Rathbun). Comp. Biochem. Physiol. 29, 671-687.
Barnes R. S. K. (1967) The osmotic behaviour of a number of grapsoid crabs
with respect to their differential penetration of an estuarine system.
J. Exp. Biol. 47, 535-551.
Blasco E. and Forward R. (1988) Osmoregulation of the xanthid crab Panopeus
herbstii. Comp. Biochem. Physiol. In press.
Cameron J. N. and Mangum C. P. (1983) Environmental adaptation of the
respiratory system: Ventilation, circulation and oxygen transport.
In The Biology of Crustacea: Environmental Adaptation (Edited by
Vernberg F. J. ana Vernberg W. B), Vol. 8, pp. 43-63. Academic Press,
New York.
Engel D.W. and Nichols C. D. (1977) A method for continuous in vivo
measurements of .haemolyrcph conductivity in crabs. J. exp. Mar. Biol.
Ecol. 26, 203-209.
Felder D. L. (1978) Osmotic and ionic regulation in several western
callianassidae (Crustacea, decapoda, Thalassinidae). Biol. Bull.
(Woods Hole, Mass.) 154, 409-429.
Gilles R. and Pequeux A. (1983) Interaction of chemical and osmotic
regulation with the environment. In The Biology of Crustacea:
Environmental Adaptation (Edited by Vernberg F. J. and Vernberg W.
B.), Vol. 8, pp. 109-178. Academic Press, New York..
Hill R. W. (1976) Comparative physiology of animals: An environmental
approach. Harper and Row, New York. pp. 1-656.
Jones L. L. (1941) Osmotic regulation of several crabs of the Pacific coast
of North America. J_. Cell Comp. Physiol. 18, 79-92.
Kenney B. E., Litaker W. , Duke C. S. and Ramus J. (1988) Community oxygen
metabolism in a shallow tidal estuary. Estuarine, Coastal and Shelf
Science 26, in press
Mangum C. and Van Winkle W. (1973) Responses of aquatic invertebrates to
declining oxygen conditions. Amer. Zool. 13, 529-541.
Monsanto Company. 1984. Lasso: Herbicide by Monsanto - Complete
Directions for Use. St. Louis, MO.
Redmond J. R. (1955) The respiratory function of hemocyanin in Crustacea.
J. Cellular Comp. Physiol. 46, 209-247.
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Skaggs R. W., Gilliam J. W., Sheets T. J. and Barnes J. S. (1980) Effects
of agricultural land development on drainage waters in the North
Carolina tide water region. Water Resources Institute of the
University of North Carolina. Report #159 (August 1980).
Smith R. I. (1967) Osmotic regulation and adaptive reduction of water
permeability in a brackish-water crab, Rhithropanopeus harrisii
(Brachyura, Xanthiaae). Biol. Bull. (Woods Hole, Mass.) 133, 643-653.
Takacs R., Forward R. B. and Kirby-Smith W. (1988) Effects of the herbicide
alachlor on larval development of the mud-crab, Rhithropanopeus
harrisii (Gould). Estuaries. In press.
Tagatz M. (1971) Osmoregulatory ability of the blue crab in different
temperature-salinity combinations. Chesapeake Sci. 12, 14-17.
Taylor A. C. (1976) The respiratory responses of Carcinus maenas to
declining oxygen tension. _J. Exp. Biol. 65, 309-322.
Taylor E. W. and Butler P. J. (1973) The behavior and physiological
responses of the shore crab Carcinus maenas during changes in
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Vernberg F. J. (1983) Respiratory adaptations. In The Biology of
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Vernberg W. B.), Vol. 8, pp. 1-42. Academic Press, New York.
Warner G. F. (1977) The Biology of Crabs. Elek Science, London.
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14
Table 1. The V^„ and P for respiration under different salinities and
02 c
alachlor concentrations
Conditions ,
Salinity Alachlor Number V ^ Figure
of trials (ul C^/s/h) (mm Hg)
10 ppt 0 ppm 4
10 ppt 10 ppm 4
10 ppt 25 ppm 2
0 ppt 0 ppm 4
0 ppt 25 ppm 2
102.8 15.9 4
109.1 28.0 5
109.3 29.0 6
134.1 24.1 7
128.3 23.8 8
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15
Figure Captions
Figure 1. Haemolymph osmolality upon acclimation to salinities ranging
from 1 to 30 ppt. Means and standard deviations are plotted.
The n for each mean is 5. The isosmotic line is plotted for
reference.
Figure 2. The time course of adjustments in haemolymph osmolality upon a
change in salinity from 20 ppt to 1 ppt. Means and standard
deviation are plotted. The n for each mean is 3. The
horizontal dashed lines show the osmolality of the 20 and 1 ppt
waters.
Figure 3. The time course of adjustments in haemolymph osmolality upon a
salinity change from 20 to 1 ppt in the presence of 25 ppm (A)
and 50 ppm (B) alachlor. Means and standard deviation are
plotted. The n for each mean was 3. The horizontal dashed
lines show the osmolality of the 20 ppt and 1 ppt waters.
Figure 4. The weight specific oxygen uptake rate (Vq£) at different oxygen
tension in 10 ppt seawater. Data from 4 trials are plotted.
The average animal weight was 0.433 g. The horizontal dashed
line represents the average V ^ for oxygen tensions between 50
and 100 mm Hg. The vertical dashed line is the position of the
critical oxygen tension (Pc)•
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16
Figure 5. The aC different oxygen tensions in 10 ppt seawater and
10 ppin (A) or 25 ppm (B) alachlor. The figure is plotted in
Figure 4, except only 2 trials were plotted in B. The average
animal weight in A was 0.363 g and B was 0.34 g.
Figure 6. The V ^ at different oxygen tensions after a salinity change
from 10 ppt to 0 ppt alone (A) for 24 h. The same experiment
was repeated in B except that crabs were also exposed to 25 ppm
alachlor. The figure is plotted as in Figure 4 except only
2 trials were plotted in B. The average animal weight in A was
0.455 g and 0.435 jn B.
-------
Acclimation Osmolality (mOsm)
-------
Time (hrs)
-------
600-
400-
E
O
E
o
o
E
CO
o
_c
Q.
E
o
E
<1)
O
X
200-
600-
400-
200-
.A
25 ppm
>20pp^^\j
1 PPt
i i
B
i i i i -
50 ppm
f T
20 pp+
"1
1 PP +
12
Time (hrs)
24
-------
Oxygen Tension (mmHg)
F'5.4-
-------
n , , ! 1 1—>
25 50 75 100 125 150
Oxygen Tension (mmHg)
Ff^.r
-------
% ( lilii
1025597
ȣl> A "1
/¦m
Oxygen Tension (mmHg)
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